A Service Agreement is the contract/agreement a user enters to with the mobile phone operator. Service agreements usually include a monthly fee and free minutes, depending on the tariff chosen.
Your HP Smart Printing Services Agreement includes the following: hardware, break/fix service, preventative maintenance, network installation, and a guaranteed quantity of toner cartridges. This is the contract governing your relationship with HP.
a business contract or agreement with a service provider to use its service for a period of time. The contract typically outlines the services provided and the costs of the services including a monthly base rate (with included minutes) and per-minute charges for minutes over the monthly maximum. In return for your commitment, a service provider will generally subsidize the initial cost of a cell phone.