Bad customer service

I am experiencing problems with Mix Telematics customer services and Accounts departments. I have forwarded them my settlement letter from SCS so to update my credit records. However, MixTelematics Account department insist that I'm still owing. My calls have been transferred to different departments and I have spent 30 minutes on the same call. They have been wasting my time and airtime because none of them are able to assist me. I was offered a 50% discount by SCS to settle my account and I paid the 50% as the remaining 50% was discounted. A settlement letter from SCS was then send to me and the account was closed on their side. When I email the same letter to Mix-Telematics, I am told I am still owing. I have been experiencing a lot of problems with Mix-Telematics and this is tiring now.