Can the Outgoing SMS plugin be modified for other sms/text services, that are free, like WhatsApp?

Hi Codee, 

I believe WhatsApp has a WhatsApp Business API, but they charge for that as well, unfortunately.

Hi Dave, I get it. Thanks.  What about utilizing Google Voice for sms? 

For any of these services, you can search to see if they have an API, and if they do, we can most likely use it.

The issue with SMS messages, though, is that the carriers themselves charge a fee, so there are typically not any free providers.  And if they offer a free trial, it's just to get you using their service or a loss leader to sell other services.

For low-volume SMS, any of the providers work because it won't cost much.  For very high-volume SMS, what some people do is route it through an actual cell phone.  Last time I checked there was Android apps available that would essentially act as a "server" that runs on a cell phone and proxies SMS messages.  That way if you have unlimited texts on your phone plan you won't pay extra.  

Thanks, Dave. That's why I was asking about Google because I've had google voice for over 20yrs and the only time I paid was for international live calling to europe. Funny, I put $25 on way back then, had 2 international students use it from my home to call France and Germany and still have $23 on it.  

Why I'm asking is this: I set up cmsb for a client and whenever an application is submitted to the backend the submitter and the site owner get confirmation emails. This customer says she is slow to pick up her emails and they get lost in all the fluff and is asking about receiving a text to her phone whenever an app is submitted. She will probably max out at 2 dozen applications per year so it's a minimal usage. She has a cellphone and she also has a google voice number so I'm trying to figure out the quickest and least expensive method to help her with that is us-based.