Where is my 40gig data?

Dear MTN, I've lost internet connection after receiving the following message:

Your Anytime data bundle is finished. Dial *136*2*999# to buy a new bundle, or *135*6# to change your out-of-bundle settings and stay connected.

How does this work? I'm on a 40gig pm contract with you, so far I've only used 2 gig. I've been without data since Friday evening. What's the problem?