Absolutely USELESS to cancel contracts making it IMPOSSIBLE to do

MTN has been a useless absolutely pathetic and I do not know what to do. We have been to agents three or four times, and we are just not getting anywhere. We are trying to cancel a month-to-month data contract that we have and for some reason the agents just are not helping us and are saying that they cannot help us. The ****le is in Johannesburg in a cupboard, as we indicated to MTN,. and we do not have access to this ****le. They are insisting that they need to phone that number and someone must answer. THIS IS A DATA CONTRACT THAT THEY GAVE US A ****LE AS A MODEM FOR INTERNET- NOT A PHONE CONTRACT. Why now phone this ****le, with no phone around, where this purported call needs to go to. MTN is so useless. The poor desk attendants cannot help us., the phone attendants say they can do nothing till we answer that damn phone number why must we now change a internet ****le router Sim card to a phone, that we do not have present where the ****le is. To receive a phone call to change and cancel this contract. In the meantime, MTN is HAPPPILYT *****ING our money every month because we tried to cancel this contract in October already and we are still billed every month. It is heartbreaking that a person must now be resorted to Hello Peter to try get some sort of reaction, but low and behold, we are probably just some drop in a bucket of complaints that they will not tend to. Does anyone have advice on how to sort thus ******** out?