This is a very common question and a 2 minute search on CSC would have given you the answer, PLEASE search before you post.
Short answer is that all you can change is the cadence of the tone, if you're expecting Metallica for internal calls and Bach for external calls that's not possible. Same tone for all calls, just different cadence.
The only other solution is to have one internal DN and one external DN so you configure the ringtone per DN, no way on the same DN.
HTH
java
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www.cisco.com/go/pdihelpdesk
HTH
java
if this helps, please rate