Telegram

On telegram, if you add contacts from your phone number, it keeps the phone number. BUT. If you add people by screen name it doesn’t give you the phone number. So I can post @gb819 right here and nobody can get my number from it. but anyone could contact me through it. You run a search with the @ sign to search for people without the phone numbers in a “secret chat.” It’s web.telegram.org if you aren’t on your phone, otherwise it’s an app.
Telegram also allows you to make large groups where everyone talks to each other.