I had huge problems with my Motorola V980 on Vodafone. It would constantly flick between 2G and 3G which if I was in the middle of a call at the time, it would cut me off. It would also often fail to receive calls at all.

I am still not sure if it was the V980 at fault or Vodafone. But I certainly wasn't happy that when they sold me the phone they said I would get a call before my contract ran out to discuss renewal but in actual fact I never got a call, it just rolled on for a few months before I realised it should have ended. Had to push support to get a refund of those missed months as I had already switched to T-Mobile anyway due to the problems above and was just waiting for the call to cancel.

To be fair though, you have to argue with all the networks to get refunds as they just blame the customer for everything, that we should KNOW the seller was lying and we have to cancel BEFORE the contract ends or it carries on indefinitely. But still, it rather put me off Vodafone.