Is there a way to lock contacts on an Iphone so my child can not change or add to them?

Yes in Restrictions. Go to Settings > General > Restrictions (enter your password for Restrictions or set it on), then on Privacy > check Don't Allow Changes.

NO. "Don't allow changes" does not prevent editing contacts. It prevents allowing other apps to access contacts.

elcpu wrote:

Yes in Restrictions. Go to Settings > General > Restrictions (enter your password for Restrictions or set it on), then on Privacy > check Don't Allow Changes.

No, that is not what it does.

I just tested this and even with restrictions on I was still able to add and delete contacts that were already in my contacts app. It just made it so I couldn't change anything with my email accounts or add contacts to my email account but I could still delete all my contacts in the contact app.I don't think that there is a way to do what you're looking for. – AJ

elcpu I just tested your suggestion and couldn't get it to work. I was still able to delete contacts in my contacts app as well as add them. Were you able to get it to work, if so how?-AJ

No. There is no way to do that other than don't let your child play with your phone.

If you want them to be able to play a game or something specific, then use Guided Access.