Missing Data Replenished

Good day, I purchased roughly 4Gigs of data last week when Vodacom had a problem with their billing. I had no idea that there was a problem thinking it was my phone I purchased roughly 4gigs all of which was for 1 week which is what I usually use. I spoke to a lady advising the situation and she said that the data would expire in 1 month and not 1 week due to the error being Vodacoms fault and that now I was sitting with over 3 gigs of data. I have a feeling that this has not been the case and my data has only lasted a week.