Thanks. I don't actually have an iPhone, so my freshly acquired "knowledge" of this was based on reading about it on the Internet and I misunderstood what I read.

I don't either, but I'm familiar with the situation from talking to people who do.

The obvious answer is to just use any of the many third-party messaging apps, but in the USA it seems like there's always someone who thinks a one minute setup process and tapping a different colored icon is too much effort.