telkom mobile false advertising

On friday 13 february I received a message from telkom mobile to purchase data on special on the *123# option so - opted to purchase the 500MB that was advertised for R20. For 2 days as I had R20.51 balance but the transaction was declined after 3 calls I was told that the 500MB was R38 so - logged a complain about the false advertizing almost a week. Later I made a follow up only to find the case closed without resolving the issue and contacting me so I told the agent to reopen the case and get a manager to call me and explain but till now. No response what is wrong telkom mobile false advertising and customer service. That sucks