Well I can tell you that any SIP program can do this, one that comes to mind is Linphone. But you do need a provider. Almost all providers deal with UDP. You might be able to find one that transmits over tcp but that’ll be a very small list. TCP isn’t reliable for VoIP, for media anyway. At best you’ll find one that encrypts the signaling over TLS, which is TCP. But audio, even if encrypted too, is done over UDP.... Source: over 1 year ago

Does Linphone (https://linphone.org/) not meet that need of cross platform (website claims versions for all major OS'es) and open source (https://gitlab.linphone.org/BC/public/linphone-desktop)? - Source: Hacker News / over 1 year ago

Similarly, you can use any SIP (VoIP) provider (e.g. VOIPo Cloud), and configure the SIP account details in your native phone app. This way you will also be able to use a SIP softphone on your computer (e.g. LinPhone on Linux or Telephone on Mac), or even a real SIP phone in your home. Depending on your SIP plan you may or may not be able to make international calls this way. Source: over 2 years ago

I heard on RFD Fonus is using linphone.org to code their service. Source: almost 3 years ago

Textnow.com is one example for online texting, and I bet you could use it on public wifi. You can use a virtual phone number (VOIP) without fees from the site. Just hope this can help a little. Source: 11 months ago

Have an independent phone service from others. You can get a SIM card for $5 U.S. (price at time of this writing) an unlocked phone -phone not linked to a phone carrier service - at textnow.com or you can get the free phone app from Google's Play Store or the Apple Store at https://www.textnow.com/downloads. If you have an locked phone (phone tied to a phone carrier service), than you may be able to ask a customer... Source: 11 months ago

As for the immediate future I highly recommend that you sign up for temporary employment agencies as soon as possible so that immediate employment can happen until you hear back from more permanent jobs. This forum's comprehensive guide can help give you guidance on signing up fast for SNAP benefits for food support, Medicaid for medical insurance, emergency shelter listings, transportation assistance, listings... Source: about 1 year ago

I recently moved to Texas from SF. I have 3 phone numbers with out of state area codes: my cell phone with https://www.h2owireless.com/ (which uses AT&T), a google voice, and a textnow.com phone number. Source: about 1 year ago

There are apps like textnow.com that will give you a free phone number with free texting. You could use that to text her from a different number. If she responds you'll know that your number was blocked on her phone. Source: about 1 year ago