Still eating on my data after 3 weeks

Still waiting on the rest of my promotional anytime data . It’s now the 24th October . My contract for cell no ***was updated on the 1st October . I received the YouTube data on the 3rd and only 8gigs of anytime data . Where my contract upgrade clearly states 20Gig YouTube and 20 gig anytime data . I’ve been given numerous reference no’s and every time it says it was resolved and if not within 48hrs I need to contact MTN again . I’m getting sick and tired of the lies at MTN . For 3 weeks I’m struggling to get the rest of my data . The other thing I want to know is why when its my new billing date . The leftover of my night data just gets taken away . Didn’t government say that this can’t happen . As I’ve paid for that data . And legally it’s mine . So why does it just get taken away and not carried over .