Some feedback - I just spent about two weeks on and off trying to get VoWIFI on Vodacom working. Turns out, after about 8 calls to support, and multiple escalations, VoWIFI still does not work on Vodacom if roaming is enabled. I was told that there is a workaround, and that the workaround would be applied to my account - still nothing, and customer care won't even respond anymore. Gave up and got a Cell C prepaid sim - VoWIFI works perfectly(!)
You have a prepaid or contract number?