Olymptrade — Not de-activating/deleting the trading account even after requesting

Hi,
I stopped using Olymptrade app within 2 days of installation and recently I received a mail from that company stating they have charged 10 USD for not being active for 180 days. I requested the customer care to delete my account by stating I no longer needed that account. But still the customer care executive asks for contact number stating the manager will call me regarding this. I mean why do I need to talk to their manager for deleting my account? I don't want them to further take any charges for the account I no longer use. Kindly take necessary action and give me a solution to come out of this app.