Hi @StefanSacrey3888 ,
Maybe this link can help you:
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cuipph/firmware/8_3_5/english/release/notes/79x5x2_835.html
Enabling a Wireless Headset
By default, the wireless headset remote hookswitch control feature is disabled. You can enable it through the Cisco Unified Communications Manager Administration application. To do so, choose Device > Phone and locate the phone you want to modify. In the Phone Configuration window for the phone, select Enable for the Headset Hookswitch Control option.
On the phone, you can verify that the feature is enabled by choosing Settings > Device Configuration > Media Configuration, and verifying that the Headset Hookswitch Control setting displays Enabled.
Regards