[otrs] Agent's phone number in signature?

Hello, In signature I can put agent's first name and last name by putting tags in it. But I want also to insert agent's direct phone number there. Unfortunatelly I don't see the "Phone number" field in agent's data, so I thought that I will put it in "Comment" or "Salutation". But what field should I use? Is it possible to do that that way? Thanks in advance for any help. -- Arek