Service cancelation impossible

On 15-11-2017 I did the self service cancelation request, since it was a 1 month notice period I set the cancelation to be completed on 15-01-2018 to make sure that no one can say I didn't give the correct amount of time. After paying for the two months I received another bill for Jan, feeling that this should not be correct I phoned and spoke to Mngadi Snenhlanhla on the 23-01-2018. She informed me that no cancelation was requested and I should fill out a cancelation request form and add to that the original date of 15-01-2018 as cancelation date and she will escalate. so I did. after another bill in FEB 2018, I phoned again this time wanting to speak to a manager, don't have his name but explained it all and forwarded both mails to him on 21-02-18 to his email ********** He promised that my service will be cancelled that same day and that I will receive a corrected bill for the cancelation on 15-01-2018. This was not the end as today on 16-03-2018 I once again received a bill for march. I called again and sent all documents to ********** and there was said that no one requested cancelation. I cannot find any number that works to contact head office and would really like my service cancelled. I made it clear that all I want to keep is my mailbox account.