Absolutely disappointing service

I've taken 3 contracts with Mtn a sim only, a cell contract and a home router. My Sim contract expired so I called in and canceled the Sim only contract and the agent confirmed that their will be no cancelation fees and then I received a invoice for R4600 stating that my cell contract is canceled and thats the cancelation fee but I didnt cancel that contract. I called in and they said I have to call retentions on monday morning when I did that they kept on transferring me to different departments until I ended up at iSon retentions which they said il get an answer by the end of the day which I still didnt get an answer. This is very disappointing for a reputable company.