Get Changed is a slang term with roots from Chicago which stands for getting killed. When you die, your body goes through various changes such as Algor Mortis and Rigor Mortis, hence the term get changed. This term started gaining recognition due to the rise of drill music from Chicago, which often has gang members talking about killing their rivals.
In Lil Durk’s ‘This Ain’t What You Want(remix)’, he says “I can't do no shows cause I terrify my city, they say I terrify my city – N*ggas get slumped, you're the first to get blamed - A n*gga try us, you're the first one to get changed” Lil Durk is pretty much saying anyone who comes at him is getting murdered in order.