T-Mobile S21 5G Warranty Exchange Problems

This is the problem…

The less then a year old Samsung Galaxy S21 5g started to receive a "No simm card found" error. I took it initially to my local T-Mobile store where a young female employee declared it was an unlocked "non" T-Mobile phone and didn't qualify for any warranty (it was and is a T-Mobile phone bought from T-Mobile on my T-Mobile account). I left in frustration and called T-Mobile who provided a new simm card back at the same store. Problem continues. Contact T-Mobile and did over the air troubleshooting. The rep decided it qualified for a warranty exchange. The rep asked about damage and other then a light ¼ scratch on the screen it was flawless. The  rep said screen scratches weren't an issue. The policy that screen scratches are acceptable is on T- Mobiles website for damage explanations. So a replacement is sent to the local store were the very helpful employee inspects the phone and said the condition is acceptable. Unfortunately after an hour he could not get the replacement phone functioning. He cancels that order and puts in for another warranty exchange replacement. The phone finally arrives at the same store. When I go in a different employee, the same female employee who told me a week earlier "it was not a T-Mobile phone" looks at the scratch (again, a light 1/4" scratch that a finger nail passes right over) and declares it damaged and therefore did not qualify for a warranty exchange. The same young man in the store that had helped me on the 1st warranty exchange was there but said it was her decision (he thought the phone was fine). I have now spent hours with T-Mobile who said they would "only" charge $99 (it should have been no cost other then a $5 fee). Not acceptable so T-Mobile shuffles me off to Assurant who after patiently listening to the whole story is going to exchange the phone for no cost (i.e. they waived the deductible). Question...why couldn't T-Mobile have resolved this? It was a tiny scratch that is explicitly allowed by T-Mobile's own policy on their website? How is it a 20-something T-Mobile store employee with attitude could summarily deny my exchange? As an aside I just spoke to an employee from that store who said they denied it because if they send it back in there is a tiny possibility that the store might be back-charged $700 for the phone so they "err" on the side of caution to protect the store's interest!