IPhone 3GS Different Battery Prob + Guarantee on Insurance Claim New Phone?

Question

Summary of Problem:
Full battery to Zero battery when charging
Full battery to Zero battery and back again when in use
Battery indicator confused constantly by large amount
Is there a guarantee on my replacment phone?
Hi,
I recently accidentally damaged my iPhone 3GS and under my insurance was sent a brand new one. The problem I had was it restarted itself 3 times a day since the first day I had it but I put this down to a software issue that might be sorted in an update. Then all of a sudden the phone gets confused about how much battery level it thinks it has, also quite often when I charge it it will suddenly turn off (as it thinks it has no battery even if it's 50% full) and I have to wait half an hour for it to turn on while it charges to 5% but then it will do it again. If I don't touch it it will usually charge ok.
Other times I could be out and when using my phone it gets to 68% then battery icon changes to 0% and it shuts off, then when turned back on it's back to 68% again and works. It's very annoying as it does this often (tho most commonly around 68%) it's most annoying when using the GPS in the car, I have 50% battery but put it on charge while I use it and after a few minutes it thinks it's dead and restarts then charges up from 0% again. This has got to be a battery cell problem surely?
The problem is that they have said that because my old phone was 15 months old, the new one has no guarantee so im basically screwed! I don't see why I should pay £10 a month for over a year for insurance to then be charged a £25 claim excess fee and be sent a faulty phone that they won't replace or repair.
Is anyone else having this restart when charging issue? Should I have at least a 3 month guarantee against manufacturer faults on this new replacement phone? 
Thanks for your help
Rob 

Answer 1

You will need to take this up with your insurance company. They should replace the phone since they sent you a defective phone.
I know that if Apple does a warranty replacement, the replacement comes with at least a 90 day warranty. I don't know what the policy is concerning phones replaced by an insurance company.