MTN falsely advertises WEEKLY DATA BUNDLE to rob it's clients

I recently bought the MTN Weekly Special offer of 1GB for R49. The week had passed and I had tried to buy this bundle again. It can only be purchased via the MyMtn app. The app kept stating that I have insufficient airtime. I had R49.90, the bundle is R49. I called the call centre and they were of no help. The reset the line twice which did not work. They asked me to call 1555, they did not tell me this is a chargeable call. My airtime then went down to R48 when i terminated the call. I then loaded another R5 which took me to R53 and the app still stated that I had insufficient airtime. What is going on with MTN? The only reason I put in R50 of airtime was to buy the bundle. What do I do now?

My mobile data is switched off because I am being charged at out of bundle rates. I cannot read my emails, Whatsapp messages or use Facebook.