Overbilling on account

I visited the Vodacom Shop in the waterfront , in January, in order to complain about my cellphone invoice - over billing USA Roaming Nov/Dec. They sent an email to the billing department. i received mail from vodacom informing me that i would be credited in January. I then got another mail in February telling me that a number of people had been over billed, and that I would be credited shortly???? It is now 12 March and after spending 28min on the line with customer care at vodacom I am no closer to being refunded.