Worst Treatment Ever!

I purchased a Dell Laptop at Balfour park mall, as I checked before purchase i found that the keypad buttons were hard, with my best of knowledge i assumed it had not been used in a while would be the best explanation. 2 weeks later the buttons stopped working and had a sticky movement. I later returned it to the store and was met with rude insults, ************ation and unwillingness to assist by the white male manager when I informed him I'm knowledgeable of my consumer rights on fair trade and that I can clearly see that this was previous water damage, and as I had no receipt as the laptop is under warranty. I called the head office to assist me to get it repaired and was sent back to the store. Once received I got a call back stating that i must pay half the amount and that the warranty doesn't cover such and was told it is my fault it was damaged even though the sales consultant and my witness can prove otherwise as I mentioned the buttons were hard on purchase, without being informed it previously had water damage. I will not be miss treated or be taken advantage off and have my rights abuse by the store employees, as I'm considering taking them to court for unfair trade and verbal abuse.