Cannot remove delegates in Skype for Business

Question

A colleague of min has somehow managed to add me as a delegate for Skype for Business. Together, we try to remove me from his list of delegates. However, we do not have this option!

It is not possible to go to [Options][Tools][Call Forwarding Settings] and the icon at the bottom of the window to go to these settings is not present (see article below)! Wonders how he has added me as a delegate in the first place.

Hope someone has a solution.

Here is a screenshop to show you that the options I need are not available (in Dutch I am afraid)

https://support.office.com/en-us/article/set-call-forwarding-options-in-skype-for-business-1ec2e7fb-471c-4c35-bc90-a35991b3f532?ui=en-US&rs=en-US&ad=US