Only on 3G after Beta 2 update.

[/macuser]

I reset network settings. It works like iOS 7 now

 

[VSMacOne]

It's happened to me a couple of times and I've had to reboot in order to get it back on 4G.

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In the iOS 6 beta, AT&T paid Apple to display "4G" instead of "3G" on the status bar of your phone. 3G is HSPA, and while I believe that HSPA+ should still be called 3G, AT&T used it to say it had the only "4G" smartphone. (This was of coarse before the iPhone 5 and LTE capabilities)
What I believe happened in the iOS 8 beta, is that AT&T must have had a contract with Apple about the "4G" name, and it recently expired. Hence the "3G" showing, as it should.
Sorry if this doesn't answer your exact question, but I found myself on this thread wondering if other people had the same thing happening to them, and thought that I may as well post so if others like me find this thread they will see my answer.

I don't think this is correct because mine switches back to 4G after I do a hard reboot. I think it has something to do with the way this beta handles the transfer between LTE and 4G. Also, when it does switch to 3G my data doesn't work at all which also points to a bug.

 

[VSMacOne]

Happened again this morning when I went out of LTE range.

 

[navodwickra]

Anybody else's iPhone 5 dropped down to 3G with beta 2?

I am on 3 Mobile UK and my 4G is fine but the 4G toggle has been disappeared.

 

[cwwilson]

This is now happening on my iPad on beta 2. I get a very reliable LTE signal here in OKC and now it only shows 3G. But the speeds still feel pretty fast.

Weird. :\

 

[jsalicru]

This happened to me last night. However, speediest results show LTE speeds for me still.

 

[MaxPayne79]

This happened to me last night. However, speediest results show LTE speeds for me still.

ya despite doing clean install a few days ago, i lost my LTE AGAIN a few hours ago.

 

[GreyOS]

I don't know if this is related, but I totally lost all mobile signal yesterday and my iPhone went a bit screwy. I tried the Airplane Mode trick, resetting with power and home button, and resetting Network settings. None of these worked, so I tried resetting all settings. The loading bar got stuck on reboot and wouldn't progress. Had to do a DFU restore to 7.1.1. Luckily this has fixed it, I was a little worried the chip might have been fried.

 

[Nixle]

I don't know if this is related, but I totally lost all mobile signal yesterday and my iPhone went a bit screwy. I tried the Airplane Mode trick, resetting with power and home button, and resetting Network settings. None of these worked, so I tried resetting all settings. The loading bar got stuck on reboot and wouldn't progress. Had to do a DFU restore to 7.1.1. Luckily this has fixed it, I was a little worried the chip might have been fried.

Got stuck also on the progress bar after trying a reset all settings, put the phone in DFU mode, get out of DFU mode, pressed the button to save my phone with icloud in iTunes and it magically booted with all settings reseted, my LTE was back and a couple of others bugs I experienced were gone too.

 

[navodwickra]

It's very odd. First the 4G option disappeared then it appeared and now it says LTE not 4G keep changing itself

 

[Blorzoga]

It happens to my 5 all the time. Restarting it seems to correct it. I'm actually not sure that it's really on 3G. It may just be the indicator. I did a speed test when it said 3G and it was returning LTE speeds. It seems to just replace "LTE" with "3G" on the top of the screen and in settings>cellular>enable "3G/LTE"