If you use Signal you may want to read this

How to use Signal without revealing your phone number
https://theintercept.com/2017/09/28/signal-tutorial-second-phone-number/

 

If not revealing your phone number is super important, I'd suggest using Wire.

 

Wire. Really That's like saying why drive an Audi when you can catch a bus.

Metadata
In May 2017, Motherboard published an article saying that the Wire servers "keep a list of all the users a customer contacted until they delete their account".
Wire Swiss confirmed that the statement was accurate, saying that they keep the data in order to "help with syncing conversations across multiple devices", and that they might change their approach in the future.
https://motherboard.vice.com/en_us/...s-everyone-youve-ever-contacted-in-plain-text

Also, Signal is an encrypted communications service.

 

Wire uses E2EE, but I had no idea they stored the metadata for so long.