[otrs] TicketFreeKey in AgentPhone.dtl as in CustomerMessageNew.dtl

I tried to create an input box for a free field in AgentPhone.dtl as I did in CustomerMessageNew.dtl, but it does not work. That is, I added the code <td align="top">$Data{"TicketFreeKeyField1"}:</td> <td align="top">$Data{"TicketFreeTextField1"} </td> to AgentPhone.dtl. Is this feature restricted only to CustomerMessageNew.dtl, or can it work for other pages and I am not using it correctly? (I am using OTRS 1.3.1.) Thanks