Why wont my text messages send or my phone connect to the internet? I'm on talkmobile.?

So, my phone wont send any text messages or connect to the internet? Flight mode is off and I still have all my texts left on my contract. I've tried an Orange SIM and that one sends messages, so it isn't the phone. Please help, best answer to anybody that helps in the slightest. Thanks in advance, Ethan.