Deleting the app essentially closes the door. It’s the scammers only real way to access your phone and manipulate you into giving sensitive info. However, if you gave all kinds of user names and passwords to things like credit cards and banking info, he/she would most likely already started bilking you. If really worried, it’s not too involved to cancel your credit card and have them issue you a fresh one. For your bank, visit them and explain your concerns. They’ll give you options.