Previously unlocked phone now locked after Samsung repair and won't unlock
Brand new ATT Galaxy Z Fold3 5G bought from individual. Unlock code provided and worked so could use phone on T-Mobile. After two months, wireless charging stopped working so sent for warranty repair to Samsung. Came back repaired but now locked again. Got unlock code from ATT website (it was same as original unlock code) but doesn't unlock phone.
After hours on phone trying to fix, ATT won't help because I don't have an account with them and Samsung not able to help because they don't control locking process.
After weeks to get it repaired and days trying to get it unlocked again, I now essentially have a $1000 brick that won't work on my chosen network. Extremely frustrated!!!
Am running out of suggestions. Would prefer to not pay 3rd-party unlock company as I fear it might be throwing good money after bad. How do I get ATT to troubleshoot unlock code that they just provided that isn't working?