Take the call but tell him right away you’re in the bathroom and are suffering from terrible diarrhea, and to please excuse any rude noises or distractions if you don’t answer his questions
Some years back I had fun with by using a “Jerky Boy” routine on a spam caller. I went full retard and then finally said I had to ask my mom if I could buy whatever the guy was trying to sell. It was fun....
On a more vulgar route, you could try the Danny deVito “Ruthless People’ routine and say that “Linda” can’t come to the phone because my $#@( is in her mouth.
Any which route, have fun and let your frustrations go...