Aastra 9480i User Manual page 211

If you enable this parameter, which is the default, pressing the Goodbye key rejects calls coming
into the phone while you are on an active call. When you disable this parameter, pressing the
Goodbye key hangs up the active call.
If you disable this feature, and the phone receives another call when an active call is already
present., the phone displays a softkey 1 as "Answer" and softkey 2 as "Ignore".
Configuring Goodbye Key to Cancel Incoming Calls
Aastra Web UI
Use the following procedure to configure the Goodbye key to cancel incoming calls on the IP
phone.
Note:
"Goodbye Key Cancels Incoming Call" is enabled by default.
1. Click Basic Settings->Preferences->General.
2. The "Goodbye Key Cancels Incoming Call" field is enabled by default. To disable this field,
uncheck the box.
3. Click Save Settings.
Model 9480i IP Phone User Guide 205