Hi armagon,
I obtained my Lumia 640 from EE in the UK on 20th May 2015, and it came with Windows Phone 8.1 Update 2 "out of the box" and also featued WiFi calling.
My current version is 8.10.15145.156 and I currently have no updates available.
Should I now expect to receive a further update to the latest release please?
Thanks!