Bad service

Bought a phone on Sunday and the guy i bought the phone from in store told me to use the phone before I could charge it cause the phone has already been charged from the factory, I should only charge the phone once the battery has depleted and that when I charge it I should switch the device off, which I did.. The battery depleted on Monday, and I charged it, it got full but I began using it the battery depleted quick and even when I wasn't using it kept on depleting, I then switch of the phone for couple of hours when I switched it back on the battery was almost low,Tuesday it did the same thing, kept on depleting faster and faster. As it was depleting it started to freeze and type things on its own.. He said if he takes the phone he is only gonna book it in for repair and I'm not getting anything, I'll have to wait till the phone comes back from the factory after the technician has went through it and saw if there's a problem or not, until then he can't help with anything. I would highly appreciate your help Then I decided I'd go to the store to inform them about this problem but when I got there I found the same guy who sold me the phone, when I explained everything to him he told me that he can't give me a refund or an exchange cause this phone is perfectly fine he doesn't see anything wrong with it. He would only book the phone in so it can be taken back to the factory then if they say it has a problem he will then assist me with any refund or an exchange and this was day 4 after I've bought the phone 7days hasn't passed yet.