Can I please get feedback

Some few weeks ago I logged in a complaint with regards to Cell C billing me even though I do not have a contract with them anymore. I received a call from some guy and he promised to follow up and provide me with feedback. I did receive a missed call from 140 number but I really can't get back to anyone who calls me from the call centre number. Please assist, Because Cell C is playing tricks with my account now. They even have an additional R35 they started debiting last month. i really do not know what they want from me. i paid off the phone I had with them and cancelled my contract. Even if i did not my contract with them ceased in April already I seriously do not know what they are really hoping to achieve because I do not even have a new cellphone from them. Pleaaaaase assist.