Using wifi for phone calls? [View all]

Here's the sitch:

1) Have a smartphone (android)
2) currently using Verizon for cell service
3) but since I'm almost always at home, I use my wifi for making voice calls (also, because no cell reception here)
4) if I got rid of Verizon, is there a way to use my cell phone number to make calls over the internet?
5) and texting, of course (so, SMS over internet)

Thanks for any guidance!