Here is why you are not getting full LTE on AT&T when using the Lumia 950 XL

Over the last few days, people have been picking up the new Lumia 950 XL unlocked from Microsoft. The phone supports many LTE bands, which is why it is surprising to see a few people complaining about not getting LTE when they insert their AT&T SIM.

To be certain, the Lumia 950 XL dual-SIM does support AT&T's LTE bands. You can see it in action in our unboxing video. So why are some users having an issue? As it turns out, it can be a complicated mess that falls mostly in AT&T's lap.

Issue #1 – Setting up the phone without a SIM installed

Many times when you get a new phone you just want to turn it on and start using it. Additionally, you may want to set up the phone and use it for a few hours without a SIM to get a feel for it before committing your SIM to the phone.

However, skipping the SIM during the initial out-of-box setup may be a bad idea. We have set up our Lumia 950 XL twice with different AT&T SIMs and never had an issue getting LTE data speeds. It seems one common denominator with those getting non-LTE data is that they added the SIM after the setup. There may be a crucial step where the phone configures the APN settings during the initial setup, so it is best to start with the SIM when you take the Lumia 950 XL out of the box.

Hey, you can always pop out the SIM after and put it on your older phone until the Lumia 950 XL meets your criteria for usage.

Issue #2 – No IMEI for AT&T

The International Mobile Station Equipment Identity or IMEI is used to ID phones on a network. Did you never notice how your AT&T account settings "knows" what phone you are using? That falls on the IMEI.

AT&T keeps a list of IMEIs for the phones they official sell and support. The Lumia 950 XL is not amongst those they sell. If you call AT&T and tell them you are having issues with your unlocked Lumia 950 XL and you give that phone's IMEI, they will tell you they can't help and your phone won't work. This, however, is not true.

Many people in our forums have simply given IMEIs from other AT&T phones. One trick is just walk into an AT&T store and copy the IMEI from the AT&T Lumia 950 floor model. Others have used their older AT&T phones.

Once AT&T has an IMEI they can work with they can add it to your account and SIM. Once their system recognizes the IMEI, the LTE data should kick in. So much for open GSM standards, right? Remember, the IMEI does not matter on your end it is just a device ID and is independent of your SIM account number.

IMEI, where?

How to get an IMEI? On Windows Phone, it is always found under Settings > System > About > More Info and it should be listed near the MND and IMS numbers.

Now call AT&T support and tell them you have a new phone but your data isn't working. Provide them with the dummy IMEI from another AT&T phone and your SIM number. They'll add it to their system, and you should be good to go.

As user coolbreeze78 remarks in a forum thread on this topic "AT&T's system seems to require a branded AT&T LTE IMEI to be listed on your account for LTE provisioning to work". Once AT&T has this IMEI in their system you should be all set.

Interestingly, this LTE IMEI requirement seems to be only an AT&T issue, which is why those on T-Mobile do not seem to have the same problems.

Wrap up

To clarify again: The Microsoft Lumia 950 XL unlocked with dual-SIM 100% works on AT&T's network with LTE (although visual voicemail seems to be missing).

If you are only getting "4G" showing in the notification area on your Lumia 950 XL instead of "LTE", there is nothing wrong with the phone. Our Lumia 950 XL and many others are rolling just fine on AT&T. However, you do need to follow one or both steps above to make it work.

Most of the time the problems seem to come from picking up a new AT&T SIM and giving AT&T the IMEI from the Lumia 950 XL. Those who are migrating from an AT&T Lumia 1520, Lumia 920 or any other AT&T phone with LTE do not have these problems.

If you need more help on this or want to read other's experiences just jump into our help and support forums!

Order page for the Lumia 950 XL from Microsoft

Did you get your Lumia 950 XL in today? Let us know in comments your experience so far!

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Daniel Rubino

Daniel Rubino is the Editor-in-chief of Windows Central. He is also the head reviewer, podcast co-host, and analyst. He has been covering Microsoft since 2007, when this site was called WMExperts (and later Windows Phone Central). His interests include Windows, laptops, next-gen computing, and watches. He has been reviewing laptops since 2015 and is particularly fond of 2-in-1 convertibles, ARM processors, new form factors, and thin-and-light PCs. Before all this tech stuff, he worked on a Ph.D. in linguistics, watched people sleep (for medical purposes!), and ran the projectors at movie theaters because it was fun.