Cancellation of phone contract ****

My phone contract ended in April, with constant monthly payments once the contract ended I visited the store to cancel my contract and all payments were complete and it was successful. However, Vodacom kept deducting money from my account even when I kept going to the store to lodge a complaint that my contract ended till this month. Yesterday they decided to lock my phone, and when I called customer care and asked what am I paying for as I cancelled my contract physically in store the agent said it wasn’t cancelled and I have to pay for what I don’t know, so that my phone can be unlocked. Their ****ming and bullying me by not cancelling my phone contract that ended in April and demand payments.