Unlocked Moto E4 Plus won't stay on LTE

[Digital Rules]

My roommates Verizon Wireless postpaid phone won't stay on LTE anymore. It randomly switches to 3g & 1x. He's not having dropped call issues on VoLTE, so it seems to stay locked onto LTE during calls. I have the exact same phone on Red Pocket Verizon & it never loses LTE, so it isn't a signal issue. Switched his phone from "Global" to "LTE/CDMA" & it made no difference. Wondering if the phone is possibly defective or anything else I should try?

Thanks!!

[veriztd]

Did your friend contact customer service for troubleshooting yet ? Hopefully, could be resolved if a feature was somehow removed or disabled in the billing system.

[Digital Rules]

Thanks, I'll have him do that & see what happens. Was going to try swapping sim cards between phones, but will try customer service first.