Vodacom is ridiculous

I b ought 2gig data at the beginning of the month. I use it on my phone, I don't download anything and don't do app upgrades, I use wifi to do that and my phone is setup to use wifi for all that. On the 17th I realised my whatsapp messages weren't going through, then I checked my balance, it was zero. Now every time I buy airtime, it disappears instantly too. This is not the first this this is happening, last year I bought 2gig data on the 1st and on the 3rd it was gone