I should have updated my original post. Late March, I tried a different dealer and I was able to get my modem upgraded to 4G, the dealer used the engineering part number AMMU7J A00A25 BA listed in the Customer Satisfaction Program 21B09. Cost after taxes was $316.46. They also charged me $393.42...
I recently bought a MY2017 Focus Electric. The previous owner did not upgrade to a 4G modem, and I think I’m too late for the upgrade kit. However, if any Ford dealer has one, I’m interested!