I recently bought a Huawei modem and a mobile data-only sim. I was able to setup port forwarding on it and could see my raspberry pi through public IP. However, if I try to access the IP from my phone, having another t-mobile connection, the request times out. This is bit strange as I can access the public IP from another phone with another provider (Lyca / KPN) but cannot access it from another t-mobile! It seems as if t-mobile is blocking access to it 's own IP.
Does anyone have any suggestions? Thanks for your time.