Is there a way to get Internet Sharing working on my Lumia Icon with a non-Verizon SIM?

[Windows Central Question]

I have been using an unlocked Lumia Icon with AT&T while I was in the States and now I am using Airtel (an African carrier) in Malawi. It's worked great on both networks ( H to H+) except Internet Sharing didn't work for either carrier. I talked to AT&T while I was using that, and they said I was all set up for Internet Sharing on their end, so it has to be something with the phone. Has anyone had success using the Icon's Internet Sharing feature on a non-Verizon SIM? Thanks for your time!