Poor service and very dishonest

I very disappointed with their poor service l had contract ended last year and according to phone call with contract department was up to date my contract was cancelled last year June now year later today l receive a call from vvm debt collectors l have been handed over know one said am owing for a year all off sudden l owe r800 and handed over. I call them they don't even have my details and why am owing because l have been handed over l should call vvm that is poor service from huge company which have been supporting for years since high school days. I will never advice a person to take single contract from vodacom.