Haven’t used this services but I keep seeing other people talking about it. From their FAQ : https://jmp.chat/faq

• Q4. How do I make a phone call with my JMP number?

The easiest way is to make a call from your Jabber app, if you are using a supporting app such as Cheogram Android, Conversations, Snikket, or Movim. Simply add a contact just as you would for messaging and then select the voice call option in your app.

• Q10. JMP currently only provides numbers in the USA and Canada. These numbers can make and receive both calls and messages with any country in the world.

https://jmp.chat/ could do this depending on where you live.

When I first heard of Beeper I thought it was interesting. But reading later that they were buying really old iPhones to jail break them for bridging with iMessage I had some doubts. Now they’re bought by the Wordpress people, who also bought Tumblr, and apparently selling user data to AI.. And from what I’ve read about bridges there is no E2EE with Matrix (what Beeper seems to use) to Signal bridge.