Technical Support Request Model, Repair Order Model, Party and Account Model, and Call Incident Model.
Return Material Authorization (RMA): Before a customer can successfully return a product the customer must call the support service and receive a RMA number that is placed on the returning package to make sure that product is associated properly to the customer and the service that is expected on the product (Return, Repair, Exchange). Most companies will just return to sender if this is not on or in the shipping box.
Product Evaluation: When a product is returned it is evaluated to determine if the warranty has been violated. It then goes further to determine if the product is repairable or is to be scrapped. To speed up service sometimes it can be determined to exchange the product rather then repair it depending on the product and issues at hand. The product may then go into inventory to away repair. Once an evaluation has been made an repair order may be issued.
Note: Exchanges are just a simple creation of a Return Sales order and a Sales Order.
Please see (Baseline Conceptual Models Commentary) for further details on what conceptual models are to be used for.