No after sales service

I had gone to the Vodacom 4 U shop in the Pavilion on Saturday to purchase a screen protector for my Tablet. Once I had purchased it I asked the lady if she could please apply it onto my Tablet and was told that she didn't know how and neither did the other staff members. So I had my friend apply it onto my Tablet, he has done this numerous times before, and as the last part of the screen protector made contact with my Tablet, it cracked. I phoned the store to query with them as to what can be done and was informed that it was my own fault and nothing can be done, despite informing the guy that no one at the shop wanted to apply the screen protector to my Tablet on the day that I had purchased it. I am not happy with the way this was dealt with and now have to fork out extra for a product that was defective.