A service level agreement (SLA) describes the service agreed between the client and the service provider, for example in the processing of customer enquiries in customer service. For example, the response time, the speed and quality of the processing, the courtesy of the employees or the satisfaction of the customers are agreed. The service provider's compliance with the SLA can be checked, for example, through quality management measures such as voice recording or a customer satisfaction analysis. In order to maintain an agreed service level, staff scheduling in particular is an important issue - because staff must ideally always be available as needed. If there are too many employees in the call centre, unnecessary costs are incurred. If too few staff are on site, for example in the event of unexpected call peaks, longer waiting times will result and accessibility will deteriorate.