Impossible to cancel

In February, after having our landline cables ****** three times in five months, and each time having a ten day repair period without landline or adsl, I took out a 24 month LTE-A contract with Telkom. However, a month later, after being burgled, we decided to sell our house and move to Marina da Gama. As the Marina does not have LTE-A coverage I phoned Telkom to cancel. I was advised to go into a Telkom store and to fill out a cancellation form. I would have to pay R700 cancellation fee. I reboxed the modem, queued for 45 minutes on Monday 28th March, finally reached the counter, filled in the cancellation form and was advised that someone would contact me within 21 working days. They refused to take in the modem. I received an SMS a short while later asking to rate my interaction at the store. I heard nothing. I have queried twice on the Telkom Facebook page. Each time I've been contacted by email, and asked to send in my details, which I've done. Nothing. I joined Telkom community, and asked there. Nothing. Finally, after the 21 days were past I phoned and was told that my cancellation form was not received and I haven't been assigned a case number. The end of the month came round, and yes, they deducted R999 from my account for the month of April. I'm really irritated because I can't get anyone in cancellations to contact me, and I'm still paying for a service I'm not using.