72 hours continuous cycle

Roughly 18 months ago my contract through 8ta/Telkom Mobile was cancelled by them as they could not provide me service at my house - I called them and technicians came out and the end result was they needed to cancel my contract. I then settled my contract, moved my number to prepaid with them and then ported it out to a new contract with a new company.I discovered recently via transunion that I am blacklisted by Telkom mobile. I immediately contacted their 081 180 call centre to query this - they said I owed them R305.18 - I found this strange as I had to settle the account before it could be moved to a prepaid number and ported out - the number is still working with the new company. Instead of disputing this I made an immediate payment to the account details they sent me as I needed this blacklisting removed ASAP as I'm travelling on wednesday and need the credit card for forex. I was then told they will send me a letter within 72 hours stating my account has been settled and they are lifting the blacklisting. I still have not received a letter, the call centre cant help me! After not even receiving an invoice saying I owe the money I am extremely disappointed and now desperate.