Nokia 7310 Supernova — phone got damaged 3rd time over one year of purchasing

I have a sincere problem with my mobile set.I had bought a handset this year on 27th February.Now within one year the set is disturbing 3rd time,First time it was a keypad problem,the keys,7,8,9 & the volume key was not working.I went to Nokia care & hey took almost two months to repair it.It was submitted on 3rd August & returned to me on 3rd September.Then after two months of it,it had got a battery problem & the sim card was not registering.I went to nokia care again & they had repaired it then & there.Now within one month it is again disturbing,with the same keypad problem.Now I have again gone to nokia care,but they are asking me to submit it again.I'll submit,but with what surity that it won't be damaged again?And they will take another two months to repair it.If within one year it is disturbing like this then what will happen in next years?So can u hhelp me out of this problem?I want the set to be replaced.Is it possible?Please do reply.