All voice airtime Gone

I have a uChoose Flexi 200.

My account was sitting on over R1000 this month and I bought two data bundles. Now i have no remaining airtime and your call centre says that the air time was used on data. This is a Voice contract and if there is no data loaded there should be no access to the internet (this is the way it has always been). There was clearly some glitch on Vodacoms side this week as I have been watching the social media pages and there are hundreds of people with this problem.

Please explain how a voice contact can use data if there is no data loaded.

Regards, Claudette Carr