An option exists in the UNS-1 configuration file to disable the interaction between the UNS-1 FMS and the MSFS ATC system. The 'JF_F28_UNS.ini' file is located in the following file directory: 

C:\Users\**USERNAME**\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\packages\justflight-aircraft-f28\work\JustFlight

Note: If this file does not exist, it will be created automatically once the fuel units are toggled between KG/LBS on the UNS-1 (can be changed via the FUEL > FUEL MENU page). 

In the 'JF_F28_UNS.ini' file there is a "SynchFplWithFsATC" parameter. With this parameter set to 1 (default), the UNS-1 will integrate with the MSFS ATC system, and will automatically set the flight's destination based on the arrival airport set within the UNS-1. With this parameter set to 0, all integration between UNS-1 and MSFS ATC system will be disabled, providing the user with full control over the ATC system.