Bad service

I bought a car cash on the 27th of September, the sales lady who was assisting me Mrs Moks refused to give me discount for cash sale on a car (R150000) Now she's refusing to give me proof of purchase or an invoice for the car that I bought. She's telling me that they have moved and don't have records, she'll ask the ladies to look for it in the file because it was done manually but don't know when it will be done. I need the proof of purchase urgently, now I'm stuck. She asked me to send picture of the disk, I did and when I reminded her about it she just ignored my text.