You could use Matrix. I’ve used that on my iPhone to make calls.
Getting friends onto Matrix would be a challenge. They are used to WhatsApp or FB Messenger and don’t want to change.
A phone # is like email. You can send email from any provider to any provider. With a phone #, you can text/call from any carrier to any carrier. I’m not on FB, so with some friends I either text or call (or occasionally email).
That’s where having an actual number is an advantage.