Bad service

Hi, can you please assist, i bought a phone on contract August 2015 with CELL C, of which it was as agreement of a 2 year contract, i was paying a monthly installment which was due to end on August 2017, so the problem is that CELL C has been still deducting money from my account for the Cellphone, it has been 2 months since this has been ongoing, i tried contacting CELL C, but they not helping me with anything instead they beating around the bush.