Vodacom international roaming unreliable. Service doesn't work at all

We have been trying to get international roaming working on one of Red VIP numbers and we havent succeeded. This has been going on for a long time and it looks like there is no one who really knows whats the issue and how to fix it. I was told to perform steps below and it didnt work:

Please be advised that HLR Sync has been issued. Please proceed to do a manual location update following these steps :

- Please switch the phone off remove the SIM card from the device.

- Re-insert the SIM card and turn the device on again.

- Do manual network location update by selecting network selections and change to manual - then choose MTN or Cell C - this will fail - then go back and choose Vodacom.

The user is currently travelling in Asia and missed a lot of Business calls, was lost several times and couldn't make calls for assistance. The same thing happened when the user was in Europe last year. Not only is this affecting Business but her safety as well.