Vodacom data

I logged two calls regarding data disappearing on my cell. The one called was made on the 30th of Aug, ref was provided, feedback was given and 1gig free data. However no reason was given as to why data is disappearing. Only sipulating that no problem was found. Another call was made on the 1Sept, because 20GB was already used on the 1st. How is this possible as it was the first day of the month?? No feedback was provided and im still waiting for a supervisor to get back to me. I am frustrated and fed up!!!