Damnit, there I go giving away state secrets again...
Vodafone introduced 3G in ... 2004, 2005? Me thinks back to the Olden Days... So it took 13 years before a carrier could conceivably turn off 2G in favour of 3G+ (XT starting without 2G in the first place notwithstanding). It probably won't be 13 years since LTE launched before 3G is turned off in favour of 4G+ but VoLTE is a mandatory prerequisite because there's no other (universally standardised) way to do voice.



