Poor service

I have a month to month home WiFi with mtn on the 18 of March I gave birth and from the hospital I went to my mother's place. I am currently on unpaid maternity leave and I did not pay on the 4 April knowing very well that month to month you used when you pay so I did not have money and had no problem because I am not at home and May was unsuccessful. I received emails saying I'm owing R1100 which I don't understand I explained the above and they telling me I have to pay there's usage. I also called customer care and the guy I spoke to said the must be a mistake with billing I am not supposed to owe anything because if I don't pay they WiFi won't active which is my understanding as well. Problem is I still receive emails telling me I am owing. Guys what is this ? What kind of a business you are running. Is it my problem that you made WiFi active while no payment received? How do I pay for something i did not use? Even now I am still at my mom's place.

Can someone please fix this or I am changing my WiFi once I get back home because there's no way I will pay for this.Number on query *** and my cell phone number is ***.