I got banned for saying stuff

I try to be a nice league player. I'm not toxic. But today when I played with my friends in a premade team, a friend told me to say neck yourself 3 times because we were playing around and he was pretending to be my leader. I said neck yourself twice and my other friends told me that that would get me banned. I stopped and said "i'm jk" and "pls" There's no reason for me to be mad at my team. After the match he reported me. I got a 14 day ban immediately. I've never been chat restricted or banned. Like I get it that you guys are trying to crack down on toxic teammates, but in my case I was banned for saying something that I was told to say to my 5 man team that isn't directed towards anyone. I didn't know that it was that bad when I was saying it. Can someone review my situation and help me out.

Update, I went and asked the four other people I played with, they didn't report me. No one reported me on my team and I said it in team chat