Threema does not rely on phone numbers. You can use it anonymously, and you can add other contacts without knowing their phone number. More details can be foun

Threema does not rely on phone numbers. You can use it anonymously, and you can add other contacts without knowing their phone number. More details can be found in the crypto whitepaper: https://threema.ch/press-files/2_documentation/cryptography_whitepaper.pdf https://threema.ch/press-files/2_documentation/cryptography_...