You would need to look at the CDR, Call Detail Records, to find that out. There is no ready made report for this.
If you have activated the CDR service parameter on CUCM, you can access the call details from the CAR portal by visiting this URL: https://<<CUCMIP>>/car/
The CUCM CDR reports are not very user-friendly, and we typically suggest opting for third-party software like Imagicle for a superior billing experience.
