[yvpan1]

To me LTE is a big waste of battery and a huge marketing ploy. As such I've always used and was happy with HSPA+ (despite the increased latencies). Battery on my phone thanks me for this.

In my experience, I believe HSPA+ coverage and reliability is far superior to LTE. YMMV.

Not sure what kind of problem you're having but actually LTE is more power efficient. Try travelling to regions like Asia Pacific and have your phone hooked to just H+ most of the time vs if you enable LTE/3G (4G/3G) mode, you'll see the difference.

[gnirkatto]

Ok you don't seem to get this, carrier specific updates are not OS updates. They are for how the phone talks to the system.

One other note, the carrier spent hours on this problem and what they said is not BS as you stated. Since you have no idea what went on, please keep that kind of comment to your self.

So maybe you can be more specific on what exactly these secret other updates on 'how the phone talks to the system' are, besides APN settings, to help clueless people like me understand?

[anon(9742832)]

Very simple APN settings manually turn thing on and off, to help the phone to interface. Carrier system updates allow the phone to do it automatically.

[cespinal]

Very simple APN settings manually turn thing on and off, to help the phone to interface. Carrier system updates allow the phone to do it automatically.

When I received my KEYone I just popped in my Sim card that was in my iPhone 7 and I was able to get LTE service however after a couple of days I called AT&T to let them know I was on a new device. After they noted this in the system and updated their settings I immediately lost Internet connectivity and LTE, after numerous calls with them they decided to just leave my settings setup as the iPhone and I was back to normal as soon as they did that. Not sure if that will help but that was my experience.

[gnirkatto]

Very simple APN settings manually turn thing on and off, to help the phone to interface. Carrier system updates allow the phone to do it automatically.

It's still not clear which mysterious 'carrier system updates' you refer to, which are supposedly different from APN settings that you get from the carrier, as long as you use a SIM card that belongs to that carrier, and regardless of your phone being locked or not, and that might get changed manually, or by the carrier from time to time.
But I suggest we end this debate, which doesn't add any value, and which may bore the others to death already.