I would've had it done on GitHub, but that should work as long as it's trivial to have a program update it for you periodically.

I did a quick search and found this:

https://www.engineersgarage.com/articles-raspberry-pi-sim900a-gsm-gprs-modem-voice-call-sms/

That's for the making-and-receiving-calls bit. I don't quite know how that'd work for wireless data.