I refuse to believe it's possible to have no complaints about a mobile phone company.
I've never had a problem with them.
Reception at my place is crap but no worse than people on other networks get round here, and in general their network coverage is fine. Meanwhile, I'm on a good tariff, I get a free phone upgrade every year, their customer service has invariably been good when I've needed to use it and because I've been with them for a while I get a small discount on my line rental. What's there to complain about?
I'm not getting that much of a discount! IIRC mine's more like 10%... 
