Stop blling after contract cancelletion

I requested my *** SmartBroadband 60GB Wireless Deal to be cancelled on 28 May 2020. Received confirmation of cancellation as per below

Dear ESAU ABU, Your request to cancel a Telkom service/s has been received.

Please keep the important information below handy for any communication with us with reference to this cancellation request.

Your case number: ***5 Service number to be cancelled: *** Kindly note that it may take up to 2 months for the billing process to be completed after cancellation due to a 30 days’ mandatory notice period required on all service cancellations.

We hope that we can be of service to you in the near future.

Please feel free to contact us should you require any further assistance. Best regards, The Telkom team

I followed up last week I got confirmation that may cancellation has been completed and I will not be billed for August. Now I have just received invoice for August.

Please help, How can I can my contact cancelled and no more bills. I have call 018180 no help