I wanted to see what you guys think or what to do?

I'm helping out a new user who just got into bitcoin. He was at an ATM and talked to the owner and said it was a 1% fee to Sell bitcoins. The machine itself didn't have any fee information. Anyhow, when he went to proceed it charged him 20% fee or a little over couple hundred dollar fee when selling 1k of btc. Afterwards, he called the number for support but all they do is hang up even after they just talked.

He's now asking what he can do and if that is even legal? But I am still skeptical as it could have been user error. Normally doesn't it say the fee even on the screen prior to confirming a sell or purchase? However, he says there was no fee warning stickers on the machine and there was no fee % warning while on screen. Any help appreciated.