Assistive Access workaround for calling unapproved numbers on iPhone

I have Assistive Access set up on my dads phone to control who he can contact. For quick context, he would fall for many scams and send money or even apply for loans. Anyways, he figured out that if he texts an approved contact with a number he wants to call, all he has to do is click on it after it goes through and it calls that number!! Yesterday he called one of those quick cash places and took out money!! How can this work around get resolved? I don't want to take the phone away completely.

[Re-Titled by Moderator]

Original Title: Assistive Access glitch