iMessage requires cellular service or not?

I recently have suffered very difficult financial problems and still have my iPhone 14 Pro and my iPad Air w/magic keyboard but am not able to pay my T-Mobile bill for the near future. I find that since I have WiFi and rarely utilize the call feature, I haven’t cared much…that is until the new imessaging features from the latest update.

Having read the user guide explanation on iMessage vs. RCS vs. SMS, it would seem that I would be able to use iMessage with other iPhone users.

There is one dedicated paragraph to each type and the last sentence for RCS and SMS states that a cellular plan is needed, whereas the last sentence in the iMessage description states only that WiFi is required but makes no reference to needing a cellular plan.

This wouldn’t be the first time I encountered some Apple passive-aggressiveness around punitive rules towards poverty so I figure it’s some coded shame keeping me from enjoying handwriting texting and other wacky formats but figured I’d ask on here to see if it’s anything besides that and don’t want to call apple support bc I’ll still likely have to read between the lines of their response as well.

Bee-tee-dubs, I still pay my 10 bucks a month for iCloud so I’m not a complete C.H.U.D.