SLAs fall into three main categories: customer-based, service-based, and multi-level agreements. A customer-based SLA is a singular agreement between a company and a provider outlining all services and service levels agreed upon by all parties. For example, a company providing a virtual phone system may offer bundled services like voice calling, video calling, and SMS messaging. All of these services are defined within a single contract, as opposed to three separate ones. A service-based SLA is the most straightforward type of agreement, as it states that all customers receive the same quality of service from the provider. Any end-user who signs a service-based agreement receives the same standard of service, regardless of their role, company, or department. These types of agreements generally give the vendor/provider an advantage. A multi-level SLA offers the highest possible customization, covering services at the corporate, customer, and service levels. The corporate-level agreement isn’t updated often, as the service standards it outlines generally do not change. The customer-level agreement covers services on a per-customer basis. The service-level section covers all the services a provider gives a company.