Need advice on where I stand with vodafone.?

[JJ123]

My contract is not due to end until November this year. The phone I have has had many problems including not getting reception when other phones do as well as many other things. I have contacted vodafone about this and they werent very helpful and the guy i got on the phone wasnt what i would call friendly or approachable! Do i have the right to a replacement phone even though im not ready to upgrade? or even still could i end my contract? My friend is on O2 and she had a faulty phone and they replaced it in a week! Is O2 simply a better network or did I just end up speaking to the wrong person? I dont understand these sort of things so any adivce would be greatly appreciated.