PayPal issue

Hello guys:

So I downloaded an app without knowing it would cost money (I only needed for on thing). As soon as I saw it cost money I deleted it but it proceeded to subscribe and it was going to charged me. Didn’t seem like a big deal so I deleted and unsubscribed. But later, I got an email that they were planning to use my dad’s PayPal account before I had unsubscribed. My question is how did they have my dad’s credentials if I had never set anything with his account? Also, how do I delete anything related to that account on my phone?

thank you