I came to apple store last monday, the reason is t...

I came to apple store last monday, the reason is touching issues. The employee told me i just need to spend $358.20 dollar, and then i can get a new iphone 6 plus. But, after one week, touching issues happen again, and this phone did not crash before, i protect very good. Why it will happen again? Are you sure you guys give me a new one? or just someone's phone is broken and you guys just fix it and then sell to customer?A new phone, a week on the phone there is a problem, you have a quality guarantee?