I had sent my old device iPhone 6 Plus to Tmobile for a trade in credit. The tracking # showed Tmobile warehouse already received it but no credit was issued. I have been contacted customer service so many times and they said they didn't receive the

‌I used the prepaid label that email to me by T-Mobile representative and the address is 840 W Sandy Lake red, Coppell, TX 75019.  They said that is the right address and they had check with all Tmobile warehousee there is no that phone. Is there anyway Tmobile still able to credit me for the trade in ?