When you finish a 50 week season of GM mode, you receive a Slammy award based on your actions during the season. For the Cancelled slammy, you need to have the most canceled promos from double booking superstars with matches then promos, and having the promos canceled from getting injured in the match.
The tricky thing is a lot of slammy’s, like most of a match type or most members of a certain class, will supersede it so you won’t get it.
To get Cancelled, I did normal singles matches for all fifty weeks, wearing down stamina to injure people. I did it with four players. I recommend immortal game difficulty for the higher injury chance. Avoid doing stipulation matches, even tag matches, and try to keep your roster at a lower size. I didn’t need to, but maybe do a cloud save around week 40, and use the other players to load up on conflicting stipulations (ie: tag matches if you accidentally did a lot, stipulations), have them trade you low stamina superstars, and give you cash if needed.
Also, try to have a mix of promises kept and broken so you don’t accidentally get the “most promises kept” and “most promises broken” slammy’s.
If you succeed, the trophy will unlock on the Slammy scene. Hope this helps!