No 3g/4g access for Xiaomi redmi 3s on Three network

Hi folks.
I seem to recall reading that someone had a similar problem with this phone but I can't find the thread.
Basically all my settings seem to be correct and I have 3g showing up on my screen as if I am connected yet there is no network connection messages popping up when I try to browse.
Apologies if this has been done to death before but I have been web chatting with various three agents and have only been told that the problem is the phone and as it it not supported by three there is nothing they can do.
So any help or advice is gratefully appreciated.