Data that was paid for removed before the 30 days expiry

About 3 weeks ago i purchases 5 gigs of data valid for 30 days. Two weeks into the 30 days i had used 2.4 gigs leaving me 2.6 gigs for the balance of the 30 days. For some unknow reason i received a email stating that they had given me a once off goodwill gesture of 5 gigs. There was no explanation as to why this was done as i still had 2.6 gigs available, which was more than enough. The problem is that while giving me the 5 gigs they removed the 2.6 gigs i still had available and that i had paid for. I have now sent 2 emails asking what the once of discretionary data was for and to find out what happened to the other 2.6 gigs that i had paid for. In true Vodacom fashion i am still waiting for a response.