My little stepsister asks me to fuck her hard in the ass in exchange for lending me her cell phone to talk to my girlfriend.

My stepparents took away my cell phone because I did very poorly in my school semester, so I have no way to communicate with my girlfriend. I ask my little stepsister to lend me her cell phone so I can talk to her. She asks me to fuck her hard in the ass, I agree and come inside that big ass.