New Trackphone Purchased On Line.

The phone stopped working. I have tried to work with trakphone several times. They sent me a new sim card. Phone still does not work. I would like to return tracphone for a replacement phone and have the remaining minuts and number transferred to the new phone.  In my last call it was impossible to hear or understand the person to whom I was speaking.  How do I go about returning and replacing this phone. I bought what I though would be a better phone and have been bitterly disappoited.  I have used tracphone for many, many years.