I'm not a techy and haven't a clue about what to do,but I've had problems with EE for ages and eventually convinced them,after a bit of aggro,they were in breach of their contract with me by not supplying a reliable network signal. I cancelled my deal with them,with no penalty ,and went to O2 a couple of months ago. No problems since. In my experience EE are shit.
That's interesting, because I'm with O2 and the carrier network they use for my phone is EE!