I've spent a bit of time looking into this, and it appears that I've let this part of the app sit untouched for quite some time. It's going to take a fair bit of work to get the background service to function under newer versions of Android and I don't presently have a lot of free time to deal with this.
To be quite honest, I didn't think anyone was still using the SMS part of my app. Even I don't use it, preferring instead to use an app called "VoIP.ms SMS". The guy who wrote this one uses PUSH notifications that don't require constant polling the way mine does, plus his interface is way more modern-looking. If you haven't already made the switch this app for your VoIP.ms
text messages yet, I really recommend that you do.
Just the same, when I get some time, I will still go to the trouble of updating the background service on this app.