Account cancelled but still being debited

My contract expired on 10/11/15. I phoned to cancel it and asked for my SIM card to be changed to prepaid.The consultant I spoke to confirmed that it will be done in the next 24-48 hrs. I also asked if I was going to be charged end of November and he said no. My reference for the call: #***. I confirm that end of November my bank account was debited R805.43! I also received a mail from Retention on 13/11/15 asking me why am I cancelling my contract and I explained why and they confirmed that the migration would be done within 48 hours. Please see email attached and ref: #***0. 31/12/15 I was debited R140.34 which I reversed. 31/01/16 I was debited again with R151.74 which I again reversed! Please can you stop the unauthorised debits. My agreement with Nashua Mobile was for an agreed amount of R664 per month. Ever since they moved me to MTN in 02/15 I only paid R664 end of Feb and since 03/15 till 11/15 I have been debited R805.43! I have queried this amount ever since and only received a credit once! I need to be refunded for incorrectly being debited R805.43 which is an amount I did not sign or agree to with Nashua Mobile.