I dropped my conventional cell carrier entirely in favour of an entirely IP based telephony solution, Skype. My Skype run in my Samsung Galaxy Tab 10.5, nothing rooted, or jail broken.
The biggest hurdle is enabling incoming calls from non-Skype users. Skype does not provide a call-in number for Canada, so you have to pay 10$ a month for a service to do this for you.
10$ a month is pretty inexpensive for a cell phone, including voice-mail with a web interface!
Once you have Skype enabled and you can use it for outgoing calls, head over to http://onekingtelecom.com/ and sign up. Tell them what number you would prefer (if any) and that’s it!
If Skype does ever provide such a service, then you can cancel that and save an additional 10$ monthly.
The only downside is that you will lose your existing number, if any.