I use GV for my twitter acct.
You can get a free phone number via Google Voice as long as you provide them an existing non-google-voice number.
I got rid of my cell phone plan 6 months ago, but used it's number as the number to launch my new google voice number. Once they text you a verification code, and you confirm, your new Google Voice number is established and it doesn't matter what you do with the number you used to establish it.
It works as a phone, for texting, sending images (up to some moderate size—I've. noticed huge images fail to send) from their mobile phone app or on a computer from voice.google.com anywhere there's wifi… some calls are a little spotty, but the service is good for being totally free (i've had 4-hour calls without issue… waiting on hold… I don't make 4-hour calls). Worst aspect of entire service if you use it as your only phone (which my cheap-ass does) is that your device may/somewhat typically only starts ringing on the 3rd or 4th actual ring, giving you almost no time to answer before going to voicemail. For free, it gets an A-… if it were a paid service, it would get a D.