FIS is not the same as
ATC. When you are in contact with
ATC, you are receiving positive air traffic control.
ATC controls your flight, assigns you altitude, heading, and speed.
ATC sequences you with other traffic and makes all separation decisions. When you are in contact with
FIS, you remain responsible for your own separation from other aircraft.
FIS provides information that helps you make decisions, but does not require you to follow specific instructions.