I am pretty sure that you cannot change the name on the ticket.
Last July I booked a flight for myself for May 08, when I booked I told the agent that I was getting married and would need my name to be my new surname when I travelled, they said I must book in the name I held at that time so I did, I then got married in November 2007 and when I called to tell them I had got married and needed the ticket name changed they said is was not possible and I would have to cancel and book a new flight paying full flight price again.
Well in the end after many arguments and e-mails they changed it but only because I was the same person and told them to refer to telephone taping because I was definately told I could do.
I think you are out of luck!