I put a new simm in my Galaxy J7 from AirvoiceWireless. I could call it, and send and receive texts. But I couldn't make outbound calls. Every once in a while, in the split second before it dialed, I saw a different number flash across the screen ( not long enough for me to write it down) and then the number I had dialed appeared. But a recorded voice always would say "call cannot be completed - please try again." I put the new AirvoiceWireless simm in my Moto G and it worked fine. I put the Moto's simm in the Samsung and I couldn't call out. So since I could see the problem stayed with the hardware, I called Samsung tech support. She was great. She walked me through clearing the system cache, then had me unhide system apps and clear the cache of 3 phone apps that appeared. No luck. Then she had me bring it up in safe mode.... voila, it worked. So she had me bring it back up in regular mode and it didn't work. She told me to uninstall whatever new third party apps had been installed but the only things installed in the last 4 months were system updates and a few little supporting things for the AirVoiceWireless simms and I didn't know how to uninstall any of those. So next she had me reset preferences on all apps. (settings -> apps -> 3 upper right dots -> Reset App Preferences) That did the trick. Whew! Now I can call out.