the worse things a sales representative can do to a customer

Recently went to buy a Toshiba Portege R835-P56x 13.3-Inch LED Laptop (Magnesium Blue) from a authorized Toshiba re-seller.

From this purchase, I learnt the hard way the worst 3-things a sales representative can do to a customer as follows:

1. Been rude to the customer after sales especially when there is some issues about the laptop;
2. Let the customer wandering and search for help themselves without follow up with them; and
3. Made the customer felt like cheated.

Currently the authorized Toshiba distributor is investigating about this so-called the great re-seller company selling Toshiba laptops, and I hope they will come back to me with a acceptable explanation on this issue.