T-Mobile refuses to credit my account for a device I returned & is now threating collections

A similar situation occurred with our account. My wife's new S23 FE phone was deactivated by T-Mobile because it was listed as stolen. the local store refused to accept it as a return because they did not have any in stock.  She sent it back to T-Mobile, it was signed for by their warehouse. They neglected to log the phone into their system, or an employee stole the phone, or signed for the box without receiving it. The result is the same. We are out one out of four S23 FE phones.