Have T-Mobile LTE service, but no LTE Data Connection?

I recently switched carriers from AT&T over to T-Mobile mainly due to their really cheap plans and a really good buy one get one deal on the brand new Samsung Galaxy S9 and S9+ phones. I was very excited to save some green on my monthly bill and to never worry about overages again! However, soon after I realized it might be a bumpy ride. I got to work the very next day after signing up with T-Mobile, got situated and checked my phone. I had 3 out of 5 bars of 4G LTE signal. I opened Facebook and nothing! I got the sad face and a reload icon. I quickly switched over to my speedtest by ookla app and ran a speed test. It did not complete and displayed a connection error. I called my wife she answered right away and the call quality was perfect! But what could be wrong? I asked around to my co-workers who had T-Mobile. They all chuckled when i told them i had made the switch over to the “UN-Carrier” and told me to have fun getting service inside.

My next course of action was to call T-Mobile support and see what could be done about my issue. The customer service with T-Mobile is quite possible the best I have ever encountered before! They are very polite and understanding to your needs. They tried many different things and got my signal quality back, but still I didn’t have any data over LTE.

I then scoured the glorious google once more. I stumbled across a post on the T-Mobile forum of all places (https://support.t-mobile.com/thread/140433). I was reminded while scouring the forum threads about the hidden codes for our cell phones!

This is verified to work on Samsung Galaxy S9+

So say you want to check what band your currently connected to. All you need to do is open your phone’s “Phone app” and dial: *#0011#. You will be greeted by a black screen with all kinds of information from the cellular radios inside your phone!

Notice that line 6 says: LTE RRC:CONN Band:12 BW:5MHz this means your phone is operating off of LTE Band 12.
The next menu you will need to access is the Cellular Customization Menu. While in your “Phone App” dial: *#2263#. You will see a numbered list.
Select: [4] LTE Band Preference (*) Menu.
Press: [9] Next Page.
Press: [1] LTE B12 to remove the (*) and disabling the band.
Now that is removed press the three vertical dots.And tap Back.
Press the three vertical dots.And tap Back again.
Press: [7] --Apply band configuration to apply new settings to your phone’s cellular radio.
Select the three vertical dots again and tap END.
Now restart your phone.
Go to your phone app and dial *#0011# to verify you are now connected to band 4.
Select the three vertical dots again and tap END.