Account Paid off but no paid up letter received

On the 06/09/2017 I paid off my Direct Axis account with the balance of R33581.60 that I received from Sabelo Mafuya and on the 24/10/2017 I sent him an email requesting a paid up letter he ignored my email, after that every day I have been receiving calls from Nimble Group from different consultant telling me that I still owe Direct Axis R8940 and when I explain to them that I paid off the account they say they will get back to me and no one never gets back to me instead they keep on calling telling me about the outstanding balance that I owe, every time I explain to them that i paid off the account and Sabelo Mafuya is the one who gave me the settlement amount.On the 15/11/2017 I sent an email to Sabelo asking him about a paid up letter he responded by giving me a number that I must call to get the paid up letter the number is always engaged i can't go through .I need my things to be sorted out and a paid up letter sent to me and call center consultant to stop calling telling about the money that I owe.