Worst experience

I bought a phone on Saturday. It turned off twice while my daughter was working on. A few hours apart. It just turned off. I'm now here at the truworths the Grove and Im told I should have taken a video of the phone acting up. as I signed the t/c. Nowhere does it say that. They expect me to leave the phone here for 4 more days so they can check the phone. Should I have anticipated that it would be unreliable and taken a video? Really? Now I'm standing here with a 3 day old phone that I'm not satisfied with. Im asking to exchange it but I'm being sent from pi**** to post.