Worse customer care between TFG and Jet

I had the worse experience at Jet St Georges Mall today in Cape Town. I purchased a few items, told the cashier I have a R500 tfg gift card that I would use for payment and the balance she should charge to my account. When she printed my receipt, she had charged the entire clothing purchase to my account and an extra R500 to the gift card. I spoke the manager and all I got was "we can't reverse the transaction because it's a gift card". I had under no circumstances told the cashier to charge an extra R500 to the gift card. She even told me I can't get the rewards for my purchases if I pay with my gift card. After the manager could not assist, I asked to be put through to customer care. More failed attempts to get this matter resolved, first to tfg customer care and then jet customer care. I ended up leaving the store to get back to work with a store assistant promising to call me back with feedback. No one called me back. I called tfg customer service again later in the day. A lady helped me and escalated the matter for "investigation". How is it that no one can assist with reversing this gift card charged to my account by a cashier, who did not even acknowledge the error and a manager that is not even willing to assist herself? I am now left waiting, extra debt I did not want and a gift card with double the value I also did not authorise. It is absolutely pathetic that I have to sit with this and for it to take this long to be resolved.