For this method, we're going to use the LTEview app (by @ProAsm) to switch from Rains default band B3 to B38.
You require these in order for the band switch to work.
1. A compatible Huawei router (Supports TDD B38 or B41 2500/2600Mhz).
Huawei routers that will work (Not all are listed)...