Powershell ActiveDirectory Rename SamAcctName

Hello!

I work on a powershell script for my Active Directory.
My mission is simple: Search every samaccountname contains uppercase and export it to a CSV and then rename the samaccountname in lowercase.

And it work with that code for extract samaccountname in uppercase :  

Get-ADUser -filter * -Searchbase 'OU=users,DC=contoso,DC=com' | ? {$_.sAMAccountname -cmatch'^[a-z A-Z .]+$'}  | Select Name | Export-csv -path C:\Users\me\username.csv -NoTypeInformation

Why "-cmatch'^[a-z A-Z .]+$'"? Cause all of my samaccountname are written like that: x.XXxxx .

Next step, i try to rename in lowercase all the samaccountname in the list of username.csv contained in Active DIrectory.
And i'm blocked with that code :

Import-Csv C:\Users\me\username.csv | foreach{Set-ADUser -identity $_-SamAccountName  $_.sAMAccountName.tolower()}

.
It doesn't work.

Can you help me? Im a newbie.

The hardest point is after executing that script in powershell,  i want to see the result in the AD.
For example: There is an oldSamAccountName: J.smiTH , after executing the script, im able to see in AD (not in the powershell console) the new Account name: j.smith in Properties->Account. Is it possible?

Thanks in advance.