I believe all shops are like this. They can't bear the loss of replacing that phone for you coz their profit is too little. So this is what they do. Either blame you or something you never did or give you a second hand phone from the beginning.

Its my habit to check the phone properly before making a purchase. Spend time there and MAKE SURE that NOTHING is wrong with the item you purchase. After all, you're spending 1-2k on the phone...that's a lot of money dude,

its weird though...I've never seen a phone that does not have enough batt to even test at the shops.