Vodacom refuse to assist with an Unknown amount due

I had contract with Vodacom years ago, cancelled it now i have an amount that has been charged to me and sitting on my credit report for years i sent an email with all my details to sort it out, keep on sending follow up emails with no progress, this discourage me to ever get a contract with Vodacom! i really want this sorted ASAP but i can not fix this if vodacom does not assist. on the 13th of Aug someone rep**** to my email and say they would get back to me in 5-7 working days... almost a month later i am still waiting. Very dissaponted!