Have to make an amendment after filling, and now I owe but I haven’t received the refund.

I filed my taxes and it was accepted, but now someone else will claim the dependent I claimed and I have received a notice from the IRS staying I need to send documentation. Initially I was going to receive money but after the amendment I will owe, but I haven’t received the refund so I can sent it plus whatever the difference is. Now I’m stuck not knowing how to handle this situation.