Why would you play as Trevor? it's like that because the plot is forcing you to swap over to Franklin.
Madrazzo is suppose to talk to him. that's why you are going to get wrecked endlessly by his mob if you play as either one of them.
So simply swap to Franklin and wait for the mission to pop up. If I remember correctly he's waiting at your crib or something like that. I know that cutscene from that mission happens in Franklin's crib.