If it says my FaceTime call has been 2GB yet I was using wifi, does that mean I have to pay?

I accidentally fell asleep during a FaceTime call and it ended up as 8 hours and 12 minutes. When looking at my call records it says the time an then 2GB. I was using wifi so I didn't think I'd have to pay but that face it told me it was 2GB worried me an I thought maybe I would have to? If someone could let me know thy would be great because if my stepmum gets a huge bill it'll be baaaaad. Thanks!