Frustrating

I have been trying to look for guidance on what to do with my situation. I was with T-Mobile for over 17 years and was talked into going with Xfinity mobile. I'm really starting to regret my change. Although I made a mistake myself I'm just looking to get past it now. I purchased a phone that could only be delivered to myself because I'm the account holder. I then shipped that new phone using USPS to my brother two states away in Colorado. Big mistake, never use USPS! The phone is now lost and the post office can't seem to find it leaving my brother without a phone. Luckily I did ensure the package with my own money and I know I will get the money for that phone. Now I am trying to get some paperwork that shows my name and the purchase of that phone that has been applied to my billing. Shouldn't be that hard! I then would like to know how we can proceed. I know I will have to pay for the phone that the US Post Office lost but can we start the whole process over?

Shouldn't the phone that is lost be locked in some way so it can't be used in case it was stolen?

Please, somebody give me some guidance in this matter!