alltel cell phone problem?

[xxxxxSleeping_Angelxxxxx]

i got a LG AX275 cell phone from alltel. i'm on my 3rd phone since october of 07. alltel refuses to give me a new phone unless i pay for it out of pocket. however will send me the same model. i'm starting to show the same problems again with this one. i can be in the middle of text and it will turn off on it's own the same with a call. it will freeze so i can't send texts or turn off so i have to take out the battery and wait a few seconds and start all over. it's aggervating. and the pic texts stalls my phone. i am scared to complain cuz i know they will just send me the same model again and i will just be calling them back in 3 weeks to complain. am i doing something wrong or is it the phone it's self. do i just call and demand a new phone and different model. i can't afford to pay for it out of my pocket