Supplementary Services are additional services that can be provided in addition to a primary service or product. These services can be used to enhance the primary service and provide additional value to the customer. Types of Supplementary Services include customer service, technical support, installation services, training, and maintenance services. Supplementary Services can be provided by a variety of sources, such as third-party vendors, manufacturers, or the primary service provider. Supplementary Services can be used to increase customer satisfaction and loyalty, as well as provide additional revenue streams.