T-Mobile iPhones prioritize cellular over Wi-Fi calling after Carrier Bundle 32.0 and iOS 11.3 updates

Have you ever been in an area with poor network coverage? This is where the Wi-Fi calling feature on your smartphone may come in handy – it allows you to make calls using Wi-Fi or wireless data connection. What's neat, your phone will automatically switch to Wi-Fi calling if it detects a weak coverage or is connected to a good Wi-Fi network. However, there's been an issue surrounding the feature on a particular set of devices – iPhones, sold by T-Mobile. Apparently, since the iOS 11.3 and Carrier Bundle 32.0 updates some T-Mobile iPhones are not switching to Wi-Fi calling before there's little to no carrier coverage.

The issue was first spotted by a number of users on Reddit, but reports of it haven't stopped ever since. Users have also acknowledged the fact they can't control when Wi-Fi calling does or does not happen, which results in an even bigger confusion. So, why did this sudden change of priorities happen? 

It's actually pretty simple to explain: because Wi-Fi calling is a carrier-specific feature, it means any change that the carrier makes will eventually end up on your device too. It seems like T-Mobile has changed the behavior of its Wi-Fi calling feature to now be used by your iPhone only when there is little to no coverage. Previously, coverage was not really a factor and you only needed a good Wi-Fi network to make such calls.

The bad thing is neither T-Mobile nor Apple have come up with an official statement regarding the change and it went under the radar for many users, which were not pleased to discover it themselves.

source: Reddit (1)(2)(3) via PiunikaWeb