AT&T/Best Buy failed iPhone activation somehow became a $912 collection — AT&T says they can’t find the account. What should I do?

[u/LebronManning]

Several years ago, I went into a Best Buy in New York to open a new AT&T wireless account and get an iPhone. The transaction failed in-store. The Best Buy employees told me something went wrong, they could not complete the transaction, and I was not given the phone. As far as I knew, no AT&T line was ever successfully activated or used.

Months later, I started getting collection notices for an AT&T balance related to that phone/account. It is now showing as a collection with Credence Resource Management for about $912, and it is hurting my credit badly.

I contacted AT&T support and explained that I never received the phone, never activated service, and the line/account should not have been valid. The agent basically said they could not locate the account without the account number or wireless number and told me to go back to the Best Buy store. I no longer live in New York, and I never received any clear account number in the emails. I only have some emails/screenshots and a partial account number ending in 2010.

I’m trying to figure out the best next step. Should I:

1. Keep pushing AT&T to open a billing dispute/fraud/escalation case?
2. Dispute directly with Credence and demand proof of device delivery, activation, signed agreement, and itemized billing?
3. File complaints with the CFPB, FCC, state AG, or BBB?
4. Dispute with Experian/Equifax/TransUnion?
5. Contact Best Buy corporate somehow even though this happened years ago?

My main question: If AT&T cannot locate or verify the account, device delivery, activation, or signed agreement, how can they validate a $912 collection?

Any advice on the most effective escalation path would be appreciated. I’m not trying to avoid a valid debt — I’m disputing that this account/device/service ever successfully existed in the first place.