LG KG245 phone problem

Hi,
i just bought this phone a few months ago and it has started to play up. It freezes at times (like a computer) and won't allow me to do anything - i.e. pressing any buttons does not work. On turning off the phone and turning on again, it doesn't not recognise my sim card and so i cannot access my address book, messages, etc. Also, at other times, if i receive a message and try to open it, it just stalls and once again doesn't allow me to do anything and i have to turn the phone on and off. Is my phone now a write off or is there something that can be done to fix it? Thanks in advance for your help!