Is there a problem with Ported numbers and VoWiFi?

[Cost Conscious]

I ported to Vodacom last night from MTN. I left MTN because VoWiFi was not working for me.

I had a test Vodacom SIM and could see that VoWiFi was working their network so I ported my number to Vodacom. Unfortunately, having now ported to Vodacom, VoWiFi is not working for the ported number.

I've tested across 3 different Android devices. In all cases:

1. For the non-ported / normal Vodacom SIM VoWiFi is working.
2. For the ported Vodacom SIM VoWiFi is not working.
3. Before porting to MTN I was with Cell C for many years and worked perfectly.

It is now dawning on me that the only constant here is that the number has been ported.

Anyone else experienced this?

Why should a ported number not support or trigger VoWiFi on the devices on either MTN or Vodacom networks?

Thanks.