I've had just about every VOIP telephone service ever since VOIP became available, including Magicjack, Vonage, Ooma, Packet8, and a few others that has gone out of business.
The most recent one that I cancelled was Ooma. Yea, I'm a cheapass because I didn't want to pay the $3-something cents every month in taxes.
Now I use Google Voice, which is completely free. You can choose any area code you want with Google Voice. If you already have a Gmail or Google account, just go to
www.google.com/voice and grab a phone number. You will also need to get a SIP device that hooks up to your telephone and router. I use the Obihai Obi202. Amazon sells it for $68 currently. I got it for $56 during a Lightning deal. Setting it up is not plug & play like the pre-packaged systems like Vonage or Ooma.
In case of power outages, I have my cordless phones, router, and Obihai on a 450VA UPS Backup, which can power all the devices for at least several hours.