READ DETAILS!!! What is a very good comeback when your EX boyfriend tells you "grow up"?

me and my friend were texting and my friend sent him a fwd saying "the next girl who texts you is your true love. you two are meant to be. no joke" then a couple seconds later i texted him and he thought me and her planned it and we did. but i dont want him to know that. so he told me: "knock it off. stop being so naive. and grow the hell up. seriously its getting old." what can i say to that? a very good comeback! thanks!!!