My phone  coverage is getting worse and worse. Indoors I get nothing and out I can sometimes message. Occasionally I can make calls but they always break up.

This isn't an issue for a remote area, it is the same in Glasgow, Edinburgh, Manchester and Dumfries.

I have cleaned the SIM and no change. Tried my partners SIM and that works fine. 

I basically have a product that is unusable. Suggestions please.