Earlier this year, and after spending months testing different SIM cards in my iPad, I discontinued a 15+ year contract with Vodafone because of their poor network coverage and switched to EE because it seemed to be the best.
Having dealt with all the networks at some point in the last year I can confirm that despite their brilliant network coverage EE's customer services are indeed the worst. Vodafone were probably the best.
In the space of 6 months I have found that EE have no place on-line to make complaints about network issues, nor do they seem to provide updates on said issues. All of which Vodafone did well.
It took me nearly a week to switch a T-Mobile SIM card to EE-4G because, despite their website clearly stating that you could do so with no effect on your contract and no matter how long you'd had your contract, the Customer Services staff would not believe this was possible.
I also got chewed out by a customer services rep having migrated my iPad from T-Mobile to EE in-store. I only wanted to cancel the old T-Mobile card (which for some reason the store could not do for me) but wound up on the phone for nearly half hour repeating the mantra "all I want to do is cancel my SIM card!"
I even wound up paying Orange to unlock an iPhone because they told me a T-Mobile or EE SIM would not work in it without doing so, something I later found out I could. Oh... and having to pay for an unlock? Vodafone did that for free.
I their 4G coverage wasn't so good I wouldn't be staying with them, if their 3G network had been half decent I'd have stayed with Vodafone. So long as I don't have to use customer services again I guess my time with EE won't be all that bad.