Changed passcode on child restrictions

I bought my grandson an iPhone and set up parental controls because he is not always in the best environment where he leaves and I didn't want the adults around him using it. I let my stepdaughter have the passcode because she needed to add her new number. I met to change it afterwards, but apparently did not. Now she is mad at me and has apparently changed the passcode and removed all the restrictions. Is there anything I can do without actually having his phone and knowing the code? I know I can always suspend his service, but I hate to punish him for something she is doing.