@strypey @Shufei It's https://jmp.chat
At the moment they can only give you a US or Canada number. It's an SMS-to-XMPP bridge, so you tell it which XMPP account you want to send/receive SMSes from (they recommend dismail.de) and you can use an XMPP client for texting.
It appears that for phone calls it's SIP? So I had to use a different client for that (I tried linphone and Twinkle) and just input a few credentials and was able to send/receive calls on it.