Call Completion is a great feature on Yealink handsets however we currently have to manually modify the provisioning template to enable it. It would be great to see this turned into an IP Phone configuration option in the management console (Like Transfer Type and other settings are in v15.5 SP1), perhaps you could squeeze this in to Service Pack 2. For those who have not used it: Call Completion on Yealink handsets means that during an internal call, if the callee is busy, the caller is prompted whether he wants to "wait" for the other extension to become available again. As soon as it is, he is notified and can initiate a call. This feature is often described as "callback if busy".