i might have overreacted about my kid's grades

so i was looking at my kids report card last night and it was not good. a couple of Cs and some Ds which is just really unlike them. they usually get all Bs or As so this was a big shock for me. we sat down to talk and it turned out they’ve been spending way too much time on social media, playing games, stuff like that. i mean i know teenagers do dumb things but my kid has always been different, better somehow. i kinda freaked out and told them i would take away their phone if this doesn’t improve next semester. looking back, maybe i was being a bit harsh? they seemed really upset by it all. now i’m not sure if i should take the phone or just let things go and hope for the best. im worried but also feeling guilty about how i handled it. will they ever forgive me?