Data missing. Ongoing trend

I have a on going history with Vodacom where by the 17th of each month my data bundle is depleated. In the past they refunded me. Last month I reported 3 times. Up to date no feedback and guess what this morning im out of data again. Vodacom just ***** the data you pay for. A customer service confirmed this morning that the sms and online checs differ. New system. He confirmed i have more than 1.15gig left. When i try to log on all data gone. Please explain. I want my data back. This is an on going trend. I want my data to be refunded. I only use after hours. No updates after hours.