ATT closed my account, sent to collections, and can't reopen and activate my mobile phone.

ATT gave me a promotional deal in February 2024 if I switched a landline at my office (account was for landline, fax line and internet) to a mobile phone and kept the fax line and internet.  I continued to receive my bill for my account which was paid automatically, and never received information about a separate account for the mobile device or a bill for the account.  I discovered that my work phone wasn't working, so I contacted ATT to see what was happening.  Turns out the person who sold me the promotional deal messed up the account, and now the phone was $600 in arrears, and was being written off as a bad debt and sent to collections. 

So I was credited a bunch of money, paid $90, and the rep tried to turn on the phone, with no luck. 3 hours on the phone and got disconnected!  Called back and talked to a rep that knew less, paid $400, and the rep said that the phone would be turned on in 8 hours. No luck.  Called back and got a rep who talked to 2 supervisors, several reps, and said that the account was "written off", my number was gone, and that the only people that could help me might be the third party collections agency, but that no one had a number, name, or any info on them.  That maybe after 60 days the number would be able to be claimed for a new account.... He gave me a number to what he hoped was the collections agency.  No luck.  A couple more hours on hold with various departments in various countries, and the same news:  ATT cannot do anything further for me, and my number is unavailable.

So just trying to figure out a way to get to a person with collections or high up at ATT who can get my business number turned back on...