Extra day's rental charge

I rented a vehicle from Europcar Centurion<br> Car was picked up 28.03.2015 and returned 29.03.2015 (before 11AM) left the keys at the Protea hotel as there was no one present at the europcar office. When the invoice came I was charged an extra day of rent and the deposit was not returned in full as 2 days rent was witheld.<br> When I enquired about it the lady that made the mistake was on leave and for some or other reason no one else could help me. The manager was also not at the office. I get promised feedback everyday but I never get any update... They still have my money and do not give me any feedback. It has been 10 days already