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How to determine if a particular phone will work on a particular carrier?

I am trying to determine what I need to cross check if a particular phone will work on a particular carrier.

The phone I am considering is the HTC ONE M9 or A9. In looking at the actual phone specs for the A9:

2G: GSM 850 / 900 / 1800 / 1900
3G: HSDPA 850 / 900 / 1900 / 2100
4G: LTE B1(2100), B2(1900), B3(1800), B4(1700/2100), B5(850), B7(2600), B8(900), B17(700), B20(800)

The carrier I am using now is Simple Mobile, a T-Mobile MVNO.

I looked up some reviews for this phone and some claimed that on T-Mobile is was not getting LTE but some other reviews say 4G works.

Simple Mobile's web site says "To receive 3G/4G/LTE data speeds, make sure it has the 1700 or 1900/AWS band; otherwise, it will only work on EDGE."

Does it mean it should support 4G LTE because the phone has LTE B1(2100) and B4(1700/2100) listed? I don't quite understand the B1, B2 etc terminology.

If not, is there a HTC phone that works well with Simple Mobile?
 
Simple Mobile's web site says "To receive 3G/4G/LTE data speeds, make sure it has the 1700 or 1900/AWS band; otherwise, it will only work on EDGE."

Does it mean it should support 4G LTE because the phone has LTE B1(2100) and B4(1700/2100) listed? I don't quite understand the B1, B2 etc terminology.
Those are different LTE bands. Same as 2G and 3G technology, LTE is divided into a number of sets of frequency bands, except there are more of them so it's more effort to work out what is compatible. If you do a web search on "LTE bands" you'll find explanations (but may wish you hadn't ;)).

Because so many of these bands are similar (but not identical) it's safer to go by band number rather than approximate frequencies. From a quick web search I found the following statement on Simple Mobile's website which includes this information:
In order to connect to the SIMPLE Mobile 4G LTE network, your device must operate on Band II, IV or in certain areas, Band 12. For 3G or other 4G service, your device must operate on Band II (1900 MHz) or IV (1700/2100 MHz). GSM devices that do not support these bands may operate at 2G (EDGE) speeds.
Since that phone supports LTE bands 2 and 4 you should be OK for LTE, and it has 1900 3G too.

That text refers to the 3G AWS (1700/2100), but I believe that T-Mobile have been shifting that band to LTE since 2015, so not supporting that (which only T-Mobile handsets ever supported) probably isn't important.

Or just use the website linked above ;)
 
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Thanks so much for the link tube517!

Hadron thanks for the detail explanation. That helps. I just use that web site to check for HTC M9 and A9 and with your explanations I think I have a better idea.

I had assumed previously as long as I get a GSM phone with the right frequencies I am all set and that's because I am still using an old HTC M7 that's 4 years old (or more). I think mine was an AT&T model unlocked and I used it on Simple Mobile and I am getting 4G.

The HTC A9 and M9 I am considering and being sold by Amazon now, is an "international version" which I had thought may be it's just a difference in the charger adapter plug but obviously it's more than that because the web site showed different compatibility for different versions. I am glad I didn't pull the trigger. The Amazon reviews are even more confusing because there are reports of people finding it working on T-Mobile 4G and others saying only 3G and some even saying only 2G. But I think the hundreds of reviews I am seeing on a particular phone offered for sale is not the reviews for that one particular product for sale, but the aggregate of all reviews for that phone model including all vendors and all versions. So I may be reading a review of someone who bought a AT&T HTC M9 when the product for sale is a HTC M9 International version.

Final question, what many vendors call an "International Version" is the same as what the WillMyCellPhoneWork.net call a "Global" submodel correct?
 
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The HTC A9 and M9 I am considering and being sold by Amazon now, is an "international version" which I had thought may be it's just a difference in the charger adapter plug but obviously it's more than that because the web site showed different compatibility for different versions. I am glad I didn't pull the trigger. The Amazon reviews are even more confusing because there are reports of people finding it working on T-Mobile 4G and others saying only 3G and some even saying only 2G. But I think the hundreds of reviews I am seeing on a particular phone offered for sale is not the reviews for that one particular product for sale, but the aggregate of all reviews for that phone model including all vendors and all versions. So I may be reading a review of someone who bought a AT&T HTC M9 when the product for sale is a HTC M9 International version.
Amazon are deadful because they often combine reviews from different models and mix them together. You really need to check the model number for the particular product.

As far as I can see there is only one US GSM version of the A9, the same for ATT and T-Mobile, so a US A9 would be fine. But looking at HTC's websites (for current models) and GSMArea (for older ones) it looks like you should avoid non-US HTCs if you want 4G coverage - even the more recent HTC 10 looks like only the US model would give you 4G. Annoying as the US models cover most of the LTE bands used in Europe. The newer U-series models look like they should work, but they are going to be more expensive (and glass backed & lack headphone jacks, which put some people off).
Final question, what many vendors call an "International Version" is the same as what the WillMyCellPhoneWork.net call a "Global" submodel correct?
Yes, I would think so.
 
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well the phone arrived today. I ordered a HTC M9 instead of the A9 because I saw a lot of bad reviews on the A9 having extremely bad battery performance.

So first thing I did was to cut down my mini SIM card from the old HTC one S phone to the nano SIM and tried it on the new phone. Call & Text works. Then I configured the APN etc...and got 4G. In checking with the http://willmyphonework.net site for HTC M9 compatibility with Simple Mobile, I got this:

HTCm9SM.jpg


So the best models to get would be either the North America Unlocked version or T-Mobile version.

This is the phone I ordered:

https://www.amazon.com/gp/product/B00V4LPCQG/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

If you look at the pictures it says "T-Mobile" on one of the covers. I assumed it's a T-Mobile version. But the phone that came in the mail does not have any T-Mobile logo on it. When I turned it on and off I hear the AT&T tone, and I see a few AT&T apps on the screen. I am wondering if this may be an AT&T phone? If so then if there is no 4G services I will not get 3G since that is not compatible.

On the device itself it says MODEL: OPJA110 SKU: 6729A I tried Googling it and some said it's a Developer's edition and some sites said it's "AT&T T-Mobile".

Is there any way to tell which "version" of M9 it is? This is confusing.
 
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