The phases are known as Kubler-Ross model. The name comes from the creator of the theory Elisabeth Kubler-Ross which describes the phases in her book On Death and Dying.

1. The first phase, through which the dissatisfied customer is going is denial. In this phase, he denies the problem or does not realize it yet. The duration of the phase can vary depending on the client situation, problem and many other factors. During this phase it is very unlikely for the customer to seek contact with the seller, but not excluded.
2. The second stage is anger. During this phase the client realizes of the problem but still did not accept it. He is frustrated by the events that occurred and is likely to seekcontact with the seller. Important for the seller in this case is to maintain self-control andpatience to wait for customers to move to the next phases. This is necessary because the customer is dissatisfied, angry and even unable to accept another opinion or soberlyto evaluate the situation. He was influenced by emotion and is very likely not to acceptthe proposed options for its solution. The timing here also varies, depending on individual factors.
3. The third phase is negotiation or bargain. In this phase, the client has regained composure and tons down. He already has a concept out of the situation or solutions and propose them to the seller. The most frequently proposed by the client would not be acceptable for the seller and it's important to maintain a balance in the situation. If the solutions proposed by the client are not acceptable to the seller, he will be forced to bargain with him or to refuse. Important thing is to keep good manners, and any refusal to be well grounded. It is unlikely at this stage to come to agreement with the client with what he will go into the next phase, namely:
4. The phase of depression. In this phase, the client has already realizes that a problem exists, he has his own solutions, but no consensus has been reached with the seller, in which he feels powerless,  apathy and indifference. In this phase, the seller is better to convince him that despite the existing problems, he is willing to help him. It is important for customer to receive the necessary care, to see that the seller understands his problem and is willing to help. Here again is unlikely to come to agreement with the client, because he won’t see the benefits of the proposals to the seller. However, for the seller is better to expose every possible solutions.
5. The last stage is acceptance. In this phase the client is ready to make a decision. He has accepted the problem and all its consequences, and is able to soberly evaluate the situation and to hear the point of view and the opinion of the seller. For the seller is extremely important toprovide the customer with all possible solutions. In this phase is likely to come to agreement between customer and seller that will leave your client with the feeling of satisfaction.