What you really need to do is go back to court to clean up your parenting orders. Why is the child being left with Mom's boyfriend while Mom works? Why isn't the child left with you?
So, you need to go back to court to fix your agreement. You should work with an attorney to do this -- you should not try to do this on your own. I suspect that you did not have an attorney when the agreement was created. These types of problems usually manifest themselves in agreements where the parties represented themselves. An experienced attorney probably would have anticipated this conflict and crafted an agreement that would dictate a resolution if not avoid the problem altogether.
The same way this problem sprouted and developed in your current agreement; the seeds of new, unforeseen problems likely will be sown and watered in your new agreement if you avoid an attorney's assistance. Do everyone -- including yourself -- a favor: work with an attorney.
You can't do anything which would violate a court order. You should go back to court and get all these issues cleaned up the right way. To do that, hire an attorney.
if you are not given the contact info for the sitter, you could refuse the visit but that is risky. but it makes certain the child is safe.
you could do a petition to terminate the visits for refusal to give the contact info. that will result in the judge ordering the contact info.
you could do a petition for contempt for failure to give the contact info. that will result in the judge ordering the contact info.
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