Contract Cancelation

My contract with MTN and it's ending on the 11 August 2023. I was advised to contact them a month before and request cancelation, otherwise they won't accept the cancelation in August instead it will be listed for the following month.

Today I call and the consultant tells me that they are charging me early cancelation of R1500 and for what good reason he couldn't say.

Please MTN I want to cancel the contract because your network is extremely bad in my area.