I'm pretty sure I would also feel the same way you feel. Did your wife also travel internationally? You have already done all the steps that we would have you complete.
Since the phone is still not connecting to LTE, we would recommend taking the phone to a local Verizon store location to get a brand new SIM card.
Find a store here http://vz.to/1zUEMVl (place a checkmark in the "Do not include Authorized Retailers".
We sincerely apologize for the frustration.
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After much searching the Apple and Verizon forums, and trying all types of resets on my iphone 7, I was able to find the working solution to allow my iPhone 7 to access LTE and cellular data again after traveling to Japan and using a Japan SIM card. The solution was posted by "Janseeksupport" in an apple discussion dated "Jan 19, 2015 12:02 PM in response to Lawrence Finch". I thought it quite important to share here in the Verizon Community Forum.
The solution is this — "Problem: use of other/foreign SIM
This solved it: Settings/General. Above "Reset" there was "Profile" - deleting this profile made the cellular data work again."
YES it works!
I had forgotten that after installing the local Japan SIM card in my iPhone 7, the Japanese carrier required the installation of a PROFILE in order for my phone to access the data network in Japan. This PROFILE was still in my iPhone after I replaced my original Verizon SIM upon returning to the USA. Even with my original Verizon SIM installed, I kept getting the message "Could not activate cellular data network...". My iPhone kept jumping between 1X and 3G, but would not connect to LTE. Sometimes the phone would not find the verizon service and indicate "No Service". Deleting the Profile that had been installed by the Japan SIM carrier allowed my original Verizon SIM to work properly again. Thank you "Janseeksupport" on the Apple discussions board!!!