If you're not satisfied, politely let the salesperson know you don't accept the offer and wish to pursue the matter further. Then, go up the chain of command, speaking with the next person who has authority to make a decision. If the seller is willing to look into your complaint, give him or her time to check with others and call you back. It may be natural to become frustrated or angry if you have to tell your story more than once. But stay calm .
Success often rests on one's ability to remain reasonable and coolheaded throughout the process.
If angry, you're more likely to present your case in a way that diverts attention away from the real issue. As long as someone in authority is willing to talk with you, it's not necessary to send a letter. But it is necessary to put your complaint in writing if you paid by credit card. In order to assert your rights, you must follow strict time limitations when requesting a chargeback from a credit card company. The procedures are explained on the back of your credit card statements.