Not taking my kids on a planned trip

I just told my 9 year old step daughter she needs to get her dads permission to walk to her grandmas. The last time she walked by herself her dad made her older brother walk with her. She went on some whole speech how she left her phone at her moms.... blah blah. Her brother here has a phone, they have a computer, you can contact their dad off the ps4. Well I just got up and she’s not in the house. And I called their dad pissed and he says I have no right to be pissed. I’m seriously considering just not taking her with us on Saturday.