I will list below as to why this is the case.
GSM Carriers (AT&T / T-Mobile) – Both can use voice and data at the same. Either on HSPA or on LTE (using VoLTE).
CDMA Carriers (Sprint / Verizon) – These carriers can only handle voice or data. Not both at the same time… Unless using VoLTE. Verizon currently has VoLTE whereas Sprint doesn’t. You may be asking – why is this? My old phone did this... which I am sure it did. A longer explanation is below.
[INFO]
The older phones had two CDMA radios put in them (such as the S3 on Sprint). One dedicated to voice -- another dedicated to data. Therefore you could do voice and data. GSM has always been one radio because that one radio can do both tasks at the same time. They got around it on CDMA by simply adding another radio in there and dedicating each one to one task.
Now they're getting rid of that second CDMA radio. So therefore you can only use talk, or data -- not both at the same time. Now if you're using VoLTE for your calls it will allow voice and data since the call will be going through LTE (as data) so it is technically then all data which would bypass this restriction.[/INFO]
This has been bothering me all night long and I can't let it go. I don't want to get into a war with you, but your data and what you said is not correct.
What you said
is true of CDMA
3G networks. They cannot talk and surf at the same time. It is
not true of CDMA
4G networks nor
4G LTE. Verizon 4G and 4G LTE phones
can talk and surf at the same time. The only exceptions I know of are the Droid Turbo and Moto X. (there might have been other phones, but those are the only 2 that I remember.) Those two phones had to have a software update called Advanced Calling 1.0. This came out the end of last year. Once the those two phones were updated with the new software, and the account had HD Voice enabled, then those 2 phones could
also talk and surf at the same time on 4G and LTE.
In the case of the Droid Turbo, I had one at the time of the update. Prior to, it could not talk/surf. After the update, it could talk/surf.
LG Phones: In the case of the LG G2 and LG G3, I know personally that both devices can most definitely talk and surf at the same time, because I used this function a lot with both phones and still use this function with the G2 every weekend. I never had to enable Advanced Voice on either phone to make them simultaneously talk and surf. They did this right out of the box from Verizon. Since I do not have the Verizon variant of the LG G4, I cannot say whether or not it can, but I have a feeling it can out of the box and I'd put money on the fact that it can out of the box. (Would someone with a VZW G4 please tell me if I'm wrong.)
Look in my siggy below. Every phone since the Droid Charge, including the Charge, could talk and surf simultaneously on 4G and 4G LTE except the Turbo. The Turbo needed the Advanced Calling update.
Please take it from someone who's lived through this entire experience. I do know what I'm talking about as I was the experimenter since my first SmartPhone in 2006.
Want to get lost on the rabbit hole, start with this link. It'll lead you to the rest of the story.
CDMA vs. GSM: What's the Difference? | News & Opinion | PCMag.com