How do I cancel a payment that is made automatically taken out my account every week and I don’t know what it’s for?

hello, just looking for some help. So I get text alerts every time there’s a transaction made with my debit card, deposits, withdrawals, purchases. For at least 2 months now, maybe more I’ve noticed that I get a text about a purchase for about $4 it’s always the same amount one time every week, and I don’t know what it’s for, I’ve tried to find out what it is and how to cancel it but one thing takes to to another and at the end I’ve gotten nowhere with it. I don’t anything auto renewal for the same reason. And kids can’t do it cuz all devices ask for my password for every purchase every time. It doesn’t seem like much money but with how price of everything is now, and it going on this long it really adds up. Any help will be greatly appreciated. Please and thank you.