Online Purchase that can't be reversed

This is the worse service ever received from a bank Im really considering closing my account and move to another bank. 4 Jan 2022 there was a online purchase on my account from Tefl Online. I have phoned to reverse this which the consultant have send me a form to be filled. After sending this form twice now everytime I explain I don't know the merchant so how can I phone Tefl if I dont know who this is? When you go on google and type Tefl Online to get 1000's of companies. So how must I know who is the culprit that took my money? Your help will be appreciated.