Struggling with VoWi-Fi activation

This morning I tried to get hold of customer care, which isn't as easy as it used to be, I was trying to get my Wi-Fi Calling provisioned/activated, the VoLTE works 100%. The consultant told me that I had to go to the Vodacom shop for that because it looks like there is something wrong with the device, which I know there isn't because I also have a MTN sim and I put that Sim in the phone and it works just fine, the VoLTE and the Wi-Fi Calling. And My other phone is dual sim with with Wi-Fi calling enabled for both sim slots and only the (again MTN sim) gets VoWi-Fi.