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This is a question I've already answered myself , so I'm posting this to hopefully save someone else time. I couldn't find the solution anywhere, and 3CX wouldn't assist because the current version of server is below their authorized support.<br />
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We had an issue where the caller ID in 3CX was adding a &quot;00&quot; in front of the number, so callbacks were not working properly. It was only occurring on our lines using SIP trunks though, not our PRI connection. After lots of testing and narrowing down, I found the culprit. {answer to follow}<br />
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This could potentially even happen on other call/phone systems that use SIP trunks?
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This is a question I've already answered myself , so I'm posting this to hopefully save someone else time. I couldn't find the solution anywhere, and 3CX wouldn't assist because the current version of server is below their authorized support.

We had an issue where the caller ID in 3CX was adding a "00" in front of the number, so callbacks were not working properly. It was only occurring on our lines using SIP trunks though, not our PRI connection. After lots of testing and narrowing down, I found the culprit. {answer to follow}

This could potentially even happen on other call/phone systems that use SIP trunks?

3CX server adding &quot;00&quot; to the caller ID?

Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, broadband telephony, and broadband phone service. The term specifically refers to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN).  Examples of the VoIP protocols are H.323, Media Gateway Control Protocol (MGCP), Session Initiation Protocol (SIP), H.248 (also known as Media Gateway Control (Megaco)), Real-time Transport Protocol (RTP), Real-time Transport Control Protocol (RTCP), Secure Real-time Transport Protocol (SRTP), Session Description Protocol (SDP), and Inter-Asterisk eXchange (IAX).

Voice Over IP

IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user.

IP Telephony

Telecommunication occurs when the exchange of information between two or more entities (communication) includes the use of technology. Communication technology uses channels to transmit information (as electrical signals), either over a physical medium (such as signal cables), or in the form of electromagnetic waves. The word is often used in its plural form, telecommunications, because it involves many different technologies.

3CX server adding &quot;00&quot; to the caller ID?

3CX server adding "00" to the caller ID?