Kulula does not read their emails and follow instructions

I phoned Kulula's call centre in early August 2018 to get a contact email address to cancel my credit card as they do not answer enquiries left on their website's contact page. The lady who answered was very rude and irritated and cut me off when I told her that I don't like her attitude because I could not hear her clearly. On the 15th of August 2018 I settled my Kulula credit card and asked that it be closed. I send the email to ********** as per instruction from their Facebook page. They rep**** on the 16th that I still owe an amount that was settled the same day and I forwarded the payment notification. I assumed that my credit card was now closed. Today I received a sms that I owe and amount for the end of September 2018. It is very difficult to get through to their call centre agents- I do not know who to contact now to cancel my credit card?