Cell c

I took a contract with cell c 2 years ago which ended December 2018 but they debited on my account.when I called in 1st feb was advised that I must give 30 days notice if cancellation which I have never done before as I had a phone with cell c before fine I understood the terms meaning end of February they will take last amount as 30 days will be 1st of March .. now it’s end of March and contract has been cancelled they debited again R687 I called in the lady ddnt help at all saying no it’s 30 days notice n when I checked my notice ended 1st of March why are they debuting again end of March coz my contract ended December or they did not cancel I.ln time due to their strike I don’t know