overcharged

on 20 April 2015 i called cell c regarding an additional amount of R75.04 on my April account. The agent that i spoke to suggested that the amount could have come from me exceeding the data/bandwidth that was allocated to me. however i explained that i did not exceed what was allocated to me. the agent then said he would refer my query somewhere to verify what my usage was for the month of March. I called again today( 23 April 2015) and was told that my query was not actioned to date. i was then told to call back at 4pm today for progress. My account will be deducted on 30 April 2015 and i don't want this to happen before this is sorted out because i will then be chasing cell c for a refund. Please help