I just activated a sim card on my brother's OPX. Check that the APN is set up correctly and that the voicemail number is active. Maybe try restarting your phone once you activate your sim card.
I used my Visa credit card for the autopay option and there wasn't an issue for me. As for the reception, I had a brief signal loss in the afternoon while on the canada line in the tunnel, but it came back pretty quickly. I didn't think much of it si...