Threatening email demanding money from Standard Bank for a service I have never used.

Standard Bank has in the past 4 months charged me for banking services I have not signed up for or used. The most recent occurrence has been with regard to an online share trading account. I downloaded the app. and almost immediately tried to delete it and have never used it. I received an email stating that I need to pay R330 by the 22nd of February to avoid further action. this is a very threatening email to receive given I've never received any communication about this account nor have i ever transacted on this account. I have tried calling, emailed both Standard Bank customer service, who acknowledged my email and escalated it to the online share trading platform and the share trading platform themselves, to which I also received an acknowledgment of email and a note saying they will get back to me within 24-48 working hours. I have yet to be contacted by anybody to understand what these charges are for and how I go about closing down this account. My first instance with being charged for a service I did not ask for was when they added an overdraft facility to my account. it took months for anyone to respond saying they will look into the matter. They eventually closed the overdraft facility but never refunded the charges associated with the facility and have ignored all my emails since. I'm not sure why they responsiveness is so poor or why they use bullying tactics when no other means was used to contact me. I would appreciate someone contacting me as soon as possible so this matter can be resolved.