my iphone is not turning on and suddenly if it turns on wifi doesnt work

my iphone 3gs 32 gig is not turning on and suddenly if it turns on wifi doesnt work , i have been in 24 month contract with 3 mobile, in melbourne australia, my contact is still not finished still one more month to go, but 3 months before, my iphone stop to work, after just one year there was no display in the screen i pay 100 dollar to fix it, than after that when i used to talk with some one iphone used to turn off automatically, now it already dead. when i visit to 3 store to know if they can fix my display problem one of the staff who was conulting with me give me option, either i have to go for another contract with another hand set other wise i need to repair by self, or i have to buy a cheap 3g set to use my sim. this was a crazy suggestion. i still have to go for one more year to finish my contract, and they told me i ahve just got one year warranty.i buy this expensive hand set that doesnt last for long. now it is dead ,there is no wifi, i thought the battery life is finsihed so i went to repairer they ask me 100 dollar for battery change, so its going to be more expesive in total. if i was able to change the battery by my self like other set than it was going to be cheap for me. but apple has high tech and protection...where we dont have easy access. leave this matter .

main point is my mobile is dead, and when it is on for few moment wifi doesnt work. any one know why is this, happening. poor apple user. i still love the apple because i am used to with it, i mean i am familiar with it..