FWIW, most monthly contract plans in the UK have unlimited calls & SMS. The main differentiator is the size of the data cap. There are charges for MMS etc though.
Even the cheapest of plans from the main networks (3, vodafone, EE, o2) - as low as £4/mo have unlimited calls & SMS now.
edit: this has been the case for quite a few years now, too.
RCS is the successor/replacement of MMS. Carriers will charge for it and that will be the end of the protocol.
It is explicitly designed to give carriers back control of messaging.
Why am I even saying this? We all remember how much fun carriers control over SMS was. It killed sms. There were never any new features. Cost made lots of stuff, such as multi party chats effectively impossible for teenagers ... It was always very unclear how much everything cost. There were "traps" with premium services, often not advertised as such. Now there's fraud with international SMSes. And things have gotten worse' several states made clear they use phones to find abortions ... And RCS is designed to bring this back. No.
