You should call Tech support and make sure your IMEI is listed with them in the system. If not it can cause these kinds of problem. The other thing also is to have them make sure your line is set up for Voice Over LTE and to make sure there are no restrictions. You can also check on the phone under SETTINGS > CELLULAR> CELLULAR DATA OPTIONS to make sure the Enable LTE is on for 'Voice & Data'.
Hope you get it to work and father isn't to upset.
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