Your phone specs look fine. The first thing I would try is to manually search for and connect to different networks. Determine is if your phone actually has data or not. Sometimes the data is just very slow. You need a "Ping" utility to test "pinging" Google's servers (18.104.22.168). If ping fails, you may want to check your APN and IPv6/4 settings. In the past there was some issue with foreign networks not understanding IPv6 and you'd have to set your phone to IPv4. Check the APN and see what it's set to. The current default is fast.t-mobile.com but sometimes epc.tmobile.com has worked better.
ping 22.214.171.124 failed under fast.t-mobile.com
changed Access Point Name to epc.tmobile.com
ping statistics: 3 transmitted, 3 received, 0% packet loss, time 3929 ms
time statistics: min 236, avg 246, max 266, mdev 17 ms
After the ping succeeded, I opened the browser and tried a couple of url's.
Able to bring up yahoo.com and google.com.
Looks good so far.
You da man.