Implementing Service Level Agreements takes time and effort. Bring people along with the process. The IT department should be the place to start first. Let your employees (customers) know how they are going to be affected by the new Service Level Agreements. There will be significant benefits. When they really need help, they will be able to get it because your team is going to differentiate between service requests. Is the firm's business halted due to this service request?
Examples of Service Level Agreement
Some Helpful approaches to implementing Service Level Agreements:
1) Implementing within IT first
a) Apply appropriate Severity Levels.
b) Escalate cases according to SLA rules.
c) Report on performance.
2) Send out the formal announcement to employees
a) Purpose of SLAs
b) How Severity Levels are applied
c) Responsibilities of support organization
d) Responsibilities of customers
e) Performance reporting
Here is a great White Paper on Implementing Service Level Agreements. See https://www.givainc.com/wp/it-help-desk-software-cloud-whitepapers.cfm