VoLTE support with T-Mobile and general call quality

[DeepSea]

I think it was mentioned in this post:

How to enable VoLTE (Voice over LTE)?

I’m not sure if other people have reported on this already, but I can confirm that during a stay in the US in September my FP2 (running Fairphone OS at that time) offered me the VoLTE option for the T-Mobile US SIM card that I was using in the second slot (4G during the stay) alongside my German SIM card in the first slot.

Although I am not sure if it had ever been enabled, so my previous statement implying that it worked may be categorized to “rumours”…