You want to identify internal and external incoming calls using a distinctive ringtone. For that you enabled distinctive ringtones for different call classes in user’s preference BUT these settings are not applied to Wair cordless phones.
You can change the ringtone directly from the settings of cordless phone. Go to the menu Settings -> Audio settings -> Ring melody where you will find 6 different ringtones.
Note that this change is applied only to Internal call class.
Note also that each of these 6 melodies are assigned by default to different call classes.
Internal = melody 1 (default, you can choose any of the 6 available melodies for Internal calls)
External = melody 1
VIP = melody 2
highpriority = melody 3
lowpriority = melody 4
Whitelist = melody 5
Blacklist = melody 6
If you want to reproduce a different melody for external calls you just need to change the type of call on Dialplan.
In this example the Wair phone will play the melody 3 which corresponds to the call class highpriority (you can insert it manually if the necessary call class is not present among the options).