MTN and Summermobile billing for a phone I don’t have

My experience has been awful.I did a phone upgrade with Summermobile on the 24th of October, it only arrived on the 17th of November. The phone only worked for a few hours then it shut down. I reported this to Summermobile and they said to take the phone to MTN store so they can book it and take to back the wear house, last year first week of December that was the last time I spoke to anyone from summermobile. MTN is billing me for a phone I don’t have I’ve call the customer care almost every day till this day still no help till this day. Can some please help with situation, if I don’t help or clarity by Monday I’m taking this further