UPS lost my package, T-Mobile wont do anything about it

I have the same thing just happen to us. We ordered 3 new phones and only 2 arrived so I called and they sent out a replacement which I thought was the end of it. 2 months later, their “investigation” showed the phone which I never received was “used” but can’t give me any details about this. They then charged me over $200 for sales tax and now I have to pay $8/month for a phone I never received because they claim I lied and stole it. I’m so furious with T-Mobile...I have no alternative but to take them to small claims court.