Have to stop pay for apps?

I have to pay 13,33€ for some app,

the money was add to my mobile opeator bill. I can not understand why and have to stop it.

You have ever given your carrier permission and/or used that you can pay for your App Store and iTunes Store purchases and more through mobile phone billing.

See this Apple article: Availability of mobile phone billing as an Apple ID payment method

https://support.apple.com/en-md/HT205102

Go to Settings/[your name]/Subscriptions, tap on the subscription that you want to cancel, and tap Cancel.

Here is a one-stop link for billing questions→Subscriptions and Billing - Official Apple Support. You can review your purchase history to see what you were charged for, cancel a subscription and request refunds.