No service internationally

My CEO is currently overseas - the moment he switches on his phone, and you try to phone him it states that "the nr does not exist". When he switches off his phone it goes to voicemail. We have no tried for more than a day to get this resolved with our direct contact at Vodacom but rebooting the phone over and over again is not helping. If this is a network problem then Vodacom needs to own up and either resolve it or admit that they are unable to deliver a service.