How do I raise a complaint?

I've used the chat and didn't get any response that explained why they've taken money out of my account. He explained the new payment protection plan fees but I'm on basic and it says free on my app. I've had no emails (in junk or otherwise) and no warning they were going to take a lump sum out of my account. Disgusting and I wish to complaint as chat was unhelpful. Is there an email or telephone number? I had a telephone number but it just hangs up when I call it. Thanks