I was able to extend the ring time to 30 seconds to avoid it going to voicemail. Dial *#61# from your phone. Tap Send.You should see a new screen that displays a bunch of information about what's getting forwarded. You should see a line under "Voice ...
I have had issues even getting service to get a SMS while in the US. I gave up after switching my USA sim and my Public Mobile sim in a few locations and never getting any signal.
