Charged for not having the product

Bad experience with MTN Supersonic.... We had Supersonic Air fibre installed about a year ago and now we finally get Fibre lines in our area so I call Supersonic a month ago to change my line from air fibre to standard fibre...speaking to the consultant everything went well when I ask how do I cancel the consultant says that they will automatically cancel the line once the new line is installed...the new line gets installed old router is removed and taken back with the technician that did the new installation and a month later bam a invoice for the air fibre as well as the new fibre line...I decided to call them to query as to why am I being charged for something I don't have and am not using l, the consultant says that I have to pay for is as I haven't sent through a cancellation email to the cancellation dep....so I explain that when I asked the when taking the new fibre I was told not to worry and if he could pull the recording because I am not will to pay for something I haven't used and don't have, in which he can't but he will get the manager to call me and still awaiting for the manager to call me .....really unhappy I have 3 contracts with them and I am cancelling all 3 and moving to a new service provider