Skype for Business Client - disable or remove Phone Tab

Lester, Thank you for your detailed response and anticipating certain condition.
Below is a screen shot to confirm your first point. The user (all of them actually) are set to PC-to-PC Only.
SfB-Users.JPG

This screenshot is to confirm the client-side configuration data received from SfB Server 2015.
TelephonyMode is disabled.
Using the Lync Basic 2013 client updated to Skype for Business v. 15.0.4787.1001
Path is C:\Users\<username>\AppData\Local\Microsoft\Office\15.0\Lync
Deleted as indicated.
Still persists. I've done this with multiple machines and multiple accounts.
This is a new deployment (my first). Server license and CALs bought, etc.
Performed install and configurations in EVAL mode.
This WAS about to go into production. After getting it Juuuust right for this set of users.
It WAS working properly before the following action items were taken in succession.
180 days were up and ran the commands to change from EVAL to FULL. Rebooted and reviewed logs just to be sure of a standard system startup (looking good, so far).
Didn't try the client at this point (didn't suspect I would need to).
Then, I applied the November 2015 Cumulative Update to the single SE/FE and to the (1) Edge servers.
Rebooted, again, things looked good.
Started client....hmmm? What's that doing there? (the Phone Tab).
Disabled A/V, goes away (and so does A/V capability), back to PC-to-PC only, Phone tab back.
Flipped to Enterprise, waited ~5 minutes, flipped back to PC-to-PC only, same thing.
Checked the server-side (yup, Enterprise Voice and the PSTN under Conferencing is disabled).
I suspect either the change to EVAL to FULL mode (seems unlikely) OR the November 2015 Update may have caused this?
Any other guidance?

Is it possible that there is a USB connected telephone device (not microphone and speakers, but an actual phone) connected to the PC's in question?  If not, I'm sorry but I'm out of ideas :(  I have 3 completely separate Skype for Business environments (and also about 5 Lync environments), and none of them have this issue.

My 3 environments are also running the November 2015 update.  The thing is, this looks like it's a problem with the CLIENT - and not the server.

You might want to check the client policies and see if there is a setting there which might be causeing the issue.  Client policies are Powershell only, so something like:

PS C:\Users\lclayton.NORAD> Get-CsClientPolicy 


Identity                                    : Global
PolicyEntry                                 : {}
Description                                 : 
AddressBookAvailability                     : WebSearchAndFileDownload
AttendantSafeTransfer                       : 
AutoDiscoveryRetryInterval                  : 
BlockConversationFromFederatedContacts      : 
CalendarStatePublicationInterval            : 
ConferenceIMIdleTimeout                     : 
CustomizedHelpUrl                           : 
CustomLinkInErrorMessages                   : 
CustomStateUrl                              : 
DGRefreshInterval                           : 
DisableCalendarPresence                     : 
DisableContactCardOrganizationTab           : 
DisableEmailComparisonCheck                 : 
DisableEmoticons                            : 
DisableFeedsTab                             : 
DisableFederatedPromptDisplayName           : 
DisableFreeBusyInfo                         : 
DisableHandsetOnLockedMachine               : 
DisableMeetingSubjectAndLocation            : 
DisableHtmlIm                               : 
DisableInkIM                                : 
DisableOneNote12Integration                 : 
DisableOnlineContextualSearch               : 
DisablePhonePresence                        : 
DisablePICPromptDisplayName                 : 
DisablePoorDeviceWarnings                   : 
DisablePoorNetworkWarnings                  : 
DisablePresenceNote                         : 
DisableRTFIM                                : 
DisableSavingIM                             : 
DisplayPhoto                                : AllPhotos
EnableAppearOffline                         : 
EnableCallLogAutoArchiving                  : 
EnableClientMusicOnHold                     : False
EnableConversationWindowTabs                : 
EnableEnterpriseCustomizedHelp              : 
EnableEventLogging                          : 
EnableExchangeContactSync                   : True
EnableExchangeDelegateSync                  : 
EnableFullScreenVideo                       : 
EnableHighPerformanceConferencingAppSharing : False
EnableHotdesking                            : 
EnableIMAutoArchiving                       : 
EnableMediaRedirection                      : 
EnableNotificationForNewSubscribers         : 
EnableServerConversationHistory             : False
EnableSkypeUI                               : 
EnableSQMData                               : 
EnableTracing                               : 
EnableURL                                   : 
EnableUnencryptedFileTransfer               : 
EnableVOIPCallDefault                       : False
ExcludedContactFolders                      : 
HotdeskingTimeout                           : 00:05:00
IMWarning                                   : 
MAPIPollInterval                            : 
MaximumDGsAllowedInContactList              : 10
MaximumNumberOfContacts                     : 
MaxPhotoSizeKB                              : 30
MusicOnHoldAudioFile                        : 
P2PAppSharingEncryption                     : Supported
EnableHighPerformanceP2PAppSharing          : False
PlayAbbreviatedDialTone                     : 
SearchPrefixFlags                           : 
ShowRecentContacts                          : True
ShowManagePrivacyRelationships              : False
ShowSharepointPhotoEditLink                 : False
SPSearchInternalURL                         : 
SPSearchExternalURL                         : 
SPSearchCenterInternalURL                   : 
SPSearchCenterExternalURL                   : 
TabURL                                      : 
TracingLevel                                : Light
WebServicePollInterval                      : 
HelpEnvironment                             : 
RateMyCallDisplayPercentage                 : 10
RateMyCallAllowCustomUserFeedback           : False
IMLatencySpinnerDelay                       : 1500
IMLatencyErrorThreshold                     : 1500

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At this stage however I'm clutching at straws - I don't know what could be the problem.

Lester, Well of course I would find something no one else has! (Yep, I'm one of them! Happens less frequently after being in IT for 20+ years, but it still pops up its head here and there)
No, no actual phone device plugged into the three different model laptops with Windows 7 Pro x64 I've tried this on.
I noticed somewhere in the diagnostics steps I took (can't remember at the moment which one) that there was a statement about a USB phone. However, it showed a disconnected state (because there isn't one!). May have been when I was applying the EnableSkypeUI  to True in powershell.
I had to put this project on the shelf for some other deliverables back at the end of 10/2015, before getting back on it this week.
Strange...perhaps one of the more recent client-side updates?
I'll check the entries of the client policy in powershell and get back to you. Probably Monday.

Well....hummm...the only differences between my client policy and the one you presented were:
EnableServerConversationHistory                True
EnableSkypeUI                                                  True

Everything else is the same.  

Man! REalllly don't want to rebuild this from scratch!
On the client-side, reviewing the configuration information, I see ExumEnabled and Controlled Phones set to TRUE
Would that have any bearing?

Good question - I've not seen or used those settings before.  Try to set them to False and see if it has any difference?  Don't forget to check Get-CsManagementStoreReplicationStatus to ensure the config has gone through, and then log the client off and back on

Lester, I opened a request at the Microsoft TechNet blog after our efforts.
Please review the below link and the comments there and let me know your thoughts.
https://social.technet.microsoft.com/Forums/en-US/28fe1652-1088-4899-983c-16eb5d2359c6/disable-dial-pad-and-voice-mail?forum=sfbfr&prof=required

Lester was very helpful in diagnosing. Accepted my own comment due to response from Microsoft TechNet forum from a MSFT CSG rep with what is purported to be  "The Answer".
A "feature" that isn't fixed yet...nor likely to be it appears.

It was a pleasure to help, and see this problem for my own eyes.  Some of our customers also run the Lync Basic client, and they've not asked "what's this funny thing for" yet, but at least we know we don't have to spend all the effort you've just spent trying to figure out why :)