Restitution questions

We received a letter stating our loved one owed $100 in court fees and restitution in the thousands that was due immediately. Obviously we don’t have that amount of money laying around and they’re in prison for the next 3 years so what is supposed to happen?

The letter mentioned the program the BOP has to pay these, but he’s still in a holding facility so he isn’t even in a prison to get these things set up. Are we supposed to just ignore the letters and allow things to happen when he gets to his prison?

We tried calling his lawyer and the number on the letter but no one has called us back. Just hoping for some insight from others who have been through it.