Pretend boyfriend to make someone not like you

So this guy (let’s call him Bill) really likes me and has being very annoying and childish. But my crush (let’s call him Toby) stole my phone and basically told Bill that we were dating. Obviously Toby being my crush, I agreed to prank Bill bc I didn’t like him and wanted him to give up and stop harassing me. Toby and I are going to pretend to date for 3 weeks before we tell Bill it was a joke. But I feel bad for Bill bc I feel like we are being mean and crushing his heart. I don’t know what to do. Please help me.