Why Can't I Receive Or Make Calls Or Messages?

I activated the phone some days ago. It was working fine, but then I needed to add minutes. I tried, it did not add them. My mother added me to our "family plan", so to speak, (the one we've been using for years) and was able to add the minutes from the airtime card we'd bought after groing through a long code entering process on the phone. Keep in mind, the phone had been working earlier. Now, all my messaqges fail to send, and when I try to make a call, the phone rings a few tiems then tries to connect me to an operator and an automatic voice says I should have a credit card on hand. I HAVE THE DAMN MINUTES ON MY PHONE, I HAVE AIRTIME! WHY IS THIS BLOODY THING REFUSING TO WORK? What the hell do I do?