I don’t know why people are downvoting you, might have better luck in something like a technology-centered community or putting some more information like what device or uses you have for it.
If you’re looking for an app for a mobile device while connected to wifi, there are a lot out there but they are all pretty sketchy in my experience (thinking like text-now which offers a free limited number to use but privacy and ad-blocking get thrown out the window). If you’re looking for a messenger that doesn’t have a number associated with it, something like matrix that was suggested should work (or whatever preference the people you communicate the most with prefer).