Lex and his wife have identical Samsung international phones. But when they travel to Richmond, VA, his wife's phone stops taking and receiving calls. What gives? Leo says it's because he bought an international phone. Each carrier supports different radios. So he can travel to somewhere in the US and those phones won't be supported. Leo recommends going to GSMArena, enter the model number, and it will tell what radios it supports. But his works while her phone doesn't. Leo says it's possible he doesn't have the exact same model, but very close. It could also be a configuration issue.
Tom bought an unlocked Samsung Galaxy S9 while he was travelling and now that he's back, it won't support WiFi calling. Leo says that Verizon supports VoLTE, so contact Verizon and ask them to turn on HD Voice. Tom can also turn it on with the MyVerizon app or the Verizon Account page.
Jesus wanted to get the second generation Motorola Moto X and he's heard that Sprint has stopped carrying them. Leo says that's because everyone is moving away from GSM and CDMA towards VoLTE versions. There's talk that if he were to buy a Sprint MVNO SIM in an unlocked Moto X, it'll work. Eventually, all phones will be compatible with all services, which is how it should be. Check out MotoMaker.com. He should also make sure he gets a phone with the right radio frequencies.
Mike got a Droid Turbo, but he can't work Internet and be on a call at the same time. Leo says that's one of the issues with the Turbo since it has only one antenna. You can't. But Verizon may be changing that in the coming months as Verizon moves to VoiceOver LTE (VOLTE). When it does, an upgrade will fix the problem. But only if VOLTE is supported in your market.
Mike would like to have a cellphone that he can use over multiple carriers. Leo says that while everyone is moving to LTE and Voice Over LTE, we're not there yet. Half the phones are CDMA, the other are GSM. Verizon has a SIM card for modern LTE supported phones that will work over any network except Sprint. And the phones are unlocked by FCC mandate. So that's probably Mike's best bet.
Rick says that he hears that with Sprint, if they upgrade to the new iPhone, they won't be able to talk and surf at the same time. Leo says that he can on AT&T and Verizon, though. Verizon moved over to Voice Over LTE and Leo thought Sprint was moving that way too, but apparently they haven't. T-Mobile will also work. Any GSM network will do it, and Leo suspects that Sprint will eventually go that way.