FISA courts issue warrants, which are court orders. All US courts have the power of the writ which means they can issue further orders to effectuate an order or ruling. So a court can order a company to assist the government in the execution of a warrant. This is pretty long-settled law.

The fact that some government agent applies for the warrant does not alter the fact that the warrant, once granted, is an order nor does it remove the power of the writ for further orders to effectuate the warrant.