Best app for sending text to and from cell using wifi

[AC Question]

I've got a locked down samsung phone from bell Canada and i am temporarily located in Florida. I have a data plan with Comcast in florida.

I don't want to pay roaming charges to the telco, so I am looking for an app to send/ receive voice/text to various cell phones in Canada and Florida using my comcast wifi.

I've tried nextplus which assigned me a 289 area code number, but it doesn't always work. Some friends don't get my messages on their Florida cell.