Contract cancellation, money still being deducted

I cancelled my contract with Cell C in December 2019 and yet Cell C is still deducting money every month. To make things worse there's another debit order being deducted by Cell C monthly and yet they're not sure why the 2nd debit order is being deducted from my bank account. Instead of solving the problem I am being ignored and an amount of nearly R700.00 monthly is being deducted from my ban account. Which I now have to request that my bank reverse the debit orders every month. Cell C is extremely unprofessional and unresponsive.