Update: T-Mobile has updated the support page with a clarification on those Wi-Fi calling enhancements. The phone now has support for Gogo inflight texting, a feature the company announced as part of Un-Carrier 7.0.
Carriers are now gradually rolling out Android 4.4.4 to a number of Samsung devices. Sprint's version of the Galaxy Note 3 started receiving an over-the-air update on Monday. Verizon's Galaxy S5 followed suit the next day.
T-Mobile's Galaxy S4 Becomes Next Samsung Device To Receive Android 4.4.4 Update was written by the awesome team at Android Police.