Imposible to close FNB account

I've been trying to cancel my petrol account since 22 May'19 through the online chat. To date it has still not been cancelled even though they let me know it would be done in 24 hours on 22 May'19.

FNB keeps charging me interest on this account however if it had been closed I wouldn't need to pay any interest.

I have now tried again today however the cue online is so long that it automatically logs you out before you even get a response from anyone. I waited almost half and hour to find out I was automatically logged out, when I logged back in all of a sudden there were responses from their agent however I literally sat and waited for a response and nothing came through. I then had to start the whole process again only to have the same thing happen to me. This whole process has wasted so much of my time and I got no where in the end.