An unhappy client of MTN. Please assist

Hi I took a pocket router at mtn and it was R270 st first and then when time went on I started paying from R450 to R590. And then I stopped paying my account and went to mtn store when I got there they said they cannot help me I must do it online. And they further said that my account shows two different numbers. I contacted them again and I spoke to the ***** department. They gave me an email I had to send my affidavit and a copy of my ID stating that I only used one number. I did that and the email was invalid. Now I'm blocked I can't even buy a car or anything like that. Please assist. My number is ***