Gas station just charged my bank account more than I spent..

I pumped gas today at a shell station and put only $20 in and went home with a bank notification that I was charged an extra $100… this has never happened before. I went back and talked to the clerk and he said “I don’t deal with that” so I called corporate and couldn’t talk to anyone. I feel so defeated I swear it’s just one thing after another! Whenever I have money it’s just gone. I’m gonna go to my bank on Monday and hopefully sort it out