My exp with Vodafone volte between 2 volte enabled phones is that when you call each other, is that you hear a engaged tone in your earpiece even though it's ringing at the other end. So I went to a Vodafone store & the 'solution' they had was to switch off the LTE slider switch option on both phones & now I can hear the original ringing sound in the earpiece. I was bluntly told their volte service is v problematic.