Payed up letter

I payed off my vodacom account that was handed over to MBD attorneys I finished that account last year August, I was promised that they will send me a payed up letter I never got any payed up letter from MBD since last year, I've been trying to contact them even on their WhatsApp channel they keep promising to email me the letter every time I spoke to one of the consultant the promising same thing, the worse part now HP attorneys are harassing me about this vodacom the claiming that my name from vodacom system it shows that I'm still owing them, I really don't know what to do know MBD is no where to be found with my payed up letter.