Accounts paid in full

Good day<br> <br> My account was initially handed over to select on line (Pty) Ltd , I paid all that I was asked to pay and asked for a settlement letter of which i still have a copy of an email received from Fiona Mohamed confirming that I owe nothing.<br> <br> Two weeks ago i got an sms from DMC (another agency appointed by Virgin Mobile) regarding the same account, I have sent the letter to them and they promised to call me back but so far no one has called. Please can some tell me if it is possible that a person can be handed over twice even after paying off what was handed over. I need this matter resolved asap I will no pay a cent especially after i was told that my account is paid in full<br>