T mobile not taking responsibility

I transferred devices from one account to another in 2023. Multiple times I contact t mobile because the devices were not transferred. I was told they would take care of it. They never did. They sent me to collections for those devices, even after they verified I contacted them about the issue. I spoke with the store manager and other store employee's with no resolution. I have been trying to get this taken out of collections and off my credit due to their error and they refuse. I have no problem paying off the devices, I just want it off my credit and the payment plan for the devices honored. The only valid reason I can come up with is the fact a family member who worked there was sexually harassed, was physically assaulted, and received multiple death threats from staff at the Yreka, Ca store, so as a punishment to my family for having the manager and other 2 employee's involved terminated for this behavior.