Ridiculous service

What a terrible service from such a big name (Hertz)…so so disappointed. I hired a car on the 6th of August and took it back on the 10th and was charged over double for extra day, which I still find strange. I have been waiting for my refund/deposit since the 10th of Aug and when I call the Cape Town office people there don’t care they say it’s my fault I should have called to say I brought the car back ( what nonsense is that?) and was promised to get an email confirmation now it’s 4 weeks no refund i have to pay interest on my credit card because of unprofessional practice by hertz stuff. Please help me get my refund as soon as possible also query the extra charge. I will also escalate the interest issue. Ref to Tax Inv ***3-1