What are the steps a service person needs to follow to meet the customer expectation? How cross-sell can be done to the dissatisfied customer/client?

A sales person must effectively satisfy the need of the client and must ensure also the after sales service be provided to them to comply this the sales representative must observe the proper rule on sales such as rule #1- customer is always right and rule #2 if customer is wrong refer to rule #1. We definitely discourage cross sale but in a situation that cannot be avoided we must stick to the above rule and ensure to the dissatisfied customer competent after sales service in the product.