Call center agents mistake costs me as Customer!

On the 15 March I requested the telkom mobile call center agent to recharge my data contract sim with 250mb of data for cell number ***<br> She ended up putting the data on the incorrect number,***) as I have two numbers and after the confirming the number with her, she still put it on the wrong number. I then had to call back and ask the agent to put the data on the correct number. I logged a case the next day, 16 March 2015 and received this ref number:***2. It is 9 April and I have received no response from them as yet, even after calling the call center last week for an update, I was told that someone will call me back. Now on my invoice for April, I see I was billed the extra R50.00 which the agent had put on the incorrect number! How am I responsible for someone else's incompetency at Telkom mobile? Someone call me back urgently this is really frustrating! ***