Following this guide, you will learn how to enable T-Mobile HSPA+ AWS bands (bands used by T-Mobile for 3G/4G HSPA+ service) on your AT&TSamsung Galaxy S4 smartphone models: SGH-i337 and Canadian SGH-i337M. This way you will be able to receive the 3G/4G HSPA+ data using a T-Mobile (and any other Canadian networks supporting AWS) SIM card. Which essentially means that your AT&T Samsung Galaxy S4 will turn into a fully functional T-Mobile Galaxy S4!

How to enableT-Mobile HSPA+ AWS Bands on AT&T Galaxy S4 smartphones:

Required files: DownloadPhone Utility app and install the phoneutil.apk.

Dial *#7284#on your phone dialer and choose Qualcomm USB Settings.Select RNDIS + DM + MODEMand tap on OK.Connect your SGS4 to your computer using a USB cable.For that ensure that you haveSamsung driversinstalled on your PC. You should be able to see SAMSUNG Mobile USB Serial Portunder Portsin Device Manager.Next, download QPST programon your PC and run the exe file to install QPST.Also, download the QCN file with AWS enabledfor SGH-i337/SGH-i337M.Run the QPST Program now on your computer and click on Add New Portunder Portstab.Select the COM port that you saw earlier in Device Manager. In case you have more than one, just try anyone of them first and click onOK.If you get a No Phonemessagethen try adding another COM port. If you see (0), then this would be the COM port you will be using.Now go to Start Clients(from tabs)> SOFTWARE DOWNLOAD.Click on the Backuptab and choose your COM port. Locate QCN file and hit Start. This step will backup your current NV memory. In case if something goes haywire, you would have the option to always restore the original NV memory.Now choose Restoretab and locate the QCN file 337_AWS.qcnyou downloaded earlier and click on Start. The process of flashing the AWS bands enabled QCN will initiate now.Your phone will reboot automatically. After that's done, you should be able to pick up AWS bands.

Try using the T-Mobile SIM in your AT&T Galaxy S4 and it will pick up HSPA+ signals from the t-m just fine!