Try WhatsApp and Google Voice. To transfer your number to Google Voice is on the web so I won't duplicate the web here. My brother uses Google Voice almost all the time.
Research call forwarding to your Google Voice number.
I live in an area where I do not have cell service. I rarely use my older cell phone, a Galaxy 3 due to this. Is there an app or a way to make wifi calling/ text using my cell phone number? I have been looking, and it seems that most apps want to use a new number, and I do not want to buy a new phone.
Thanks
RMR

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic