Hi David,Thank you for using Just Answer my name is Carl and I will try and help with your question.I am sorry to hear you are having problems with your phone. Do you have the samsung kies software?The software is available here http://www.samsung.com/uk/support/usefulsoftware/KIES/JSPI think the phones firmware might be the problem the kies software has a function to reinstall the firmware. I would advise backing up the phone using the kies software then reinstalling the firmware. Hopefully this will solve the problem if however after you have reinstalled the firmware the phone seems no better it is likely to be a hardware fault within the phone. I think that the S3 came with a 24month warranty if your phone is less than 24 months you should be able to get it repaired under warranty.