In an elevator installation, an elevator control system is configured to receive an elevator call from a person via a call terminal and from a robot via a radio transceiver. A current transport capacity of the elevator installation is determined. An elevator call originating from the robot is recognized by the elevator control system, the call including a priority level set by a dispatcher, wherein the priority level is one of a high, a medium and a low priority range, wherein the elevator call is indicative of a boarding floor. The allocation of the elevator call originating from the robot to the elevator car is delayed if the priority level is set to the medium priority range and the current transport capacity is lower than a first threshold value, or if the priority level is set to the low priority range and the current transport capacity is lower than a second threshold value.