In october last year i bought an Iphone 3G from vodafone and almost after a month the phone stopped working as it totally froze with no buttons working and after submitting it to vodafone store it took them 15 days to repair it and also put scratches on the phones back side and almost about 2 weeks later the phones application stopped working (not the pre installed but those which we install) and when i submitted it again they gave me a lame reason that in iphone certain applications have a limited time which is totally false since my family has a couple more of iphones and they never suffered any such kind of problem and when i contacted the head department they said they will take 14-15 days and even that time is up, i am without my iphone, no information whether it is going to repaired/replaced? when will i have it?
Since the beginning i hav asked for a replacement but the company has been refusing to do so.
What should i do?

Thanks