First instalment

I have bought a car early February in Audi and discussed with them that the first instalment should be end of March, to my surprise on the 29th of February they deducted the first instalment and I was not happy simple because the car was still with them (the dealer). Now I was negotiating with them to reverse since I was not aware and they tolled me they regret to tell me there is nothing that they can do with the issue and I am really not happy with the finance lady simple because she is the one that is telling me that she tolled me that the first instalment will be on the 29th of February 2016 and now it is my word against hers and the I-contract they said I need to sign before the price increase of the car now it is the one they said it was the contract from the bank. The contract I had is not signed and they saying the is no need to sign if I have signed the I-contract and I was sitting with this knowing and thinking I still have to sign.