Share your experience!
Double check the APN settings, also contact you Tmobile regarding 4G coverage.
I've seen that this work for other users
Settings > more > mobile networks > access point names > access point names > T-mobile > apn ptotocl > IPv4
It'll be wise to get a brand new SIM card
also do you have stamina mode on?
Any antivirus? or taskillers?
uninstall it and check agian