You need to use your real phone number for direct calls.
This is how it works:
- Request calls first
- Enter your phone number in Settings -> Account
- Enter your client's phone number in the specified profile field
When you need to call someone, click on a phone icon and the system dials your phone number first, you pick up and then it dials your client's phone number - he/she will see your actual phone # as if you called directly.