You can't change any of the tones within CUCM with custom .wav files.
If you wanted to play something like "I'm busy call later", that's not possible (at least not on CUCM side)
You would need to play that directly with CUC after it has reached VM, just upload the recording to the busy greeting.
HTH
java
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www.cisco.com/go/pdihelpdesk
HTH
java
if this helps, please rate