Here is more on getting your SLA written.
1) Definition of terms. Do not assume that everyone will know what you are talking about. You need to define terms to the lowest common level. Be as specific as possible.
2) Service delivery elements
a) Service coverage times. State clearly what business hours are supported and what is supported after hours. Failure to do this will mean you can be called at any time of the night for the most minor of problems or requests. Be sure to consider the various time zones you cover. Keep consistent and list the time zone you are in (e.g., 7AM – 7PM EST).
b) Environment(s) included. What do you cover? If you only support standard hardware and software, be sure to state it here.
c) Environments excluded. If the Support Center will take cases for non-standard hardware and will charge back costs to the customer, then list that here.
d) Specific applications and network services coverage. List specific applications by name, the times they are supported and the times they are not supported. If there are maintenance windows for databases and servers when they will not be available, then make sure to list these windows.
e) Methods for requesting service. For example, for all level 1 and 2 cases the request for service may be via the phone. For example, for level 3 and 4 cases the request for service shall only be via the Web.
f) Customer responsibilities. Some examples are: How to submit a request, what standards are supported, and when customers should be available for the technician.
g) Service tracking and reporting procedures. Some examples are: IT will log 100% of all requests, phone calls will be randomly recorded for quality and performance metrics will be posted on the web.
Here is a great White Paper on Implementing Service Level Agreements. See https://www.givainc.com/wp/it-help-desk-software-cloud-whitepapers.cfm