Samsung Galaxy S4 has started arriving in the hands of millions of smartphone customers and the T-Mobile version of the handset is now getting a minor firmware update from the carrier.

"Beginning May 7, the Samsung Galaxy S 4 will have a software update to Android version 4.2.2/Baseband version M919UVUAMDL via OTA and Samsung Kies. This update improves the Visual Voicemail app and includes ISIS app improvements," per T-Mobile support page.

The update brings improvements for the Visual Voicemail app, as well as to the ISIS app, which is used for Near-Field Communications (NFC) payments. The file size of the firmware is 168 MB and you should have at least 50 percent battery charge when starting the download process.

T-Mobile is not the only carrier which has rolled out a software update to the recently-launched Galaxy S4. U.S. carrier AT&T also started rolling out a software update, which is expected to bring smoother animations and faster performance to the handset. However, at just around 20MB, the size of the AT&T software update is quite a bit smaller when compared to T-Mobile.

U.S. is not the only country where Samsung Galaxy S4s are getting software updates. A recent report indicates that Samsung released a small software update for the handset in India. The update is available in India over-the-air and weighs under 54MB. The update is expected to improve the stability of the Galaxy S4.

Samsung seems to be very quick to release software updates to the Galaxy S4. Many rumors are surfacing in the smartphone space about the upcoming Android 4.3 Jelly Bean and Android 5.0 Key Lime Pie. It is anybody's guess how swiftly Galaxy S4 will get Android 4.3 Jelly Bean or Android 5.0 Key Lime Pie.