What is the relationship between your tail number and air traffic control?
Sometimes your callsign is your tail number, particularly on General Aviation flights. For example, if you are flying the Cessna 152 with tail number &quot;N123AB&quot;, you would call ATC with &quot;November-One-Two-Three-Alpha-Bravo&quot;.
Commercial flights, on the other hand, tend to use their flight number as the callsign. E.g. if an aircraft is operating for Delta Air Lines flight 123, the callsign would be &quot;Delta-One-Two-Three&quot;. This is not applicable to GA as GA do not usually fly a particular route or for a particular company. Assigning a flight number to every GA flight would be troublesome, it is simpler to just use your tail number as it is guaranteed to be unique.
Controllers may identify a plane by tail number when you are on the ground, but once in the air it is almost impossible to sight a plane this way. If this is your initial call to the controller, you would describe your location, which allows the controller to identify you on the radar screen. If the controller is unsure, you may be assigned a squawk code and even asked to push the IDENT button. You may also describe your type to the controller, like:

&quot;Tower, N123AB is Cessna 152, 5 miles South of XYZ, (...)&quot;

You are correct that if you do lie about your callsign, ATC as no way of knowing it unless somebody sees you, as described in the &quot;Inside Air Force One&quot; documentary by National Geographic when they tried to pretend to be a GulfStream aircraft to secretly transport the president. If you have ADS-B installed ATC will be able to see your callsign as it was programmed into the ADS-B unit, but even that can be re-programmed.