I am making a MDT system and have been getting along well until I hit a brick wall trying to figure out how to have the function 'CallJoined(Callout);' be triggered when the player accepts a call (or even better if it could be triggered when the game sends it as the notification, before the player accepts or denies it), does anyone have any idea how to do it? It seems possible because I've seen some other plugins do it but I can't seem to find how to do it myself.

In the API.Events class you should find all the events necessary to register for new callouts (including notifications).

Ok, that is working great, thank you!