ABSA refusing to close my account

I have been receiving high bank charges from Absa. Someone called and told me there are charges for using the mobile app. I requested the closure of the account. The lady told me that someone was gonna call me. A month passed and I called in to close the account in the beginning of the month. They told me I now have to pay the bank charges that I had accumulated since the account was not closed. They said someone will call me to explain more. It’s two weeks now and I haven’t received the call. I’m getting messages saying they will take legal action if I don’t pay the bank charges for last month.