Cannot use International Roaming

This is on behalf of my father. He left for overseas for India & Australia a few weeks back and had previously enabled International Roaming on his MTN mobile number (contract, not prepaid). Roaming has always worked for him on his past travels to India & Australia. However this time its not working at all and impacting his ability to do banking (or use any other OTP-linked services etc) and stay reachable on this number by his business & contacts back in South Africa.

He has tried contacting MTN via online, e-mail and phone to urgently resolve this and enable roaming, but has had no response so far and it has been over a week.