pathetic service by vodacom

Vodacom has given me grief for the last 2 years. Data number ********** 780. I have upgraded my contract n took a promotional package in 2016. To date my billing is not soughted out. They credit me n then billing goes back to normal. I'm getting msgs that I'm in arrears when I make my payment every month. In September 2018 I requested that my contracts be cancelled . N still nothing done.a the