Changing JAL return ticket destination?

Does anyone know whether it's possible to change the destination of a roundtrip ticket with Japan Airlines?

I recently came over via JAL from Canada, and my return date is at the end of September. However, I would like to fly to London instead of Canada at an earlier date using that ticket. Is this possible?

Does JAL have a English speaking phoneline in Japan?

Thank you!

Of course it varies on what fare class your ticket is but what I did when I had to change ticket dates before is I got on Skype and called the toll-free number of the country I purchased my ticket from.

It usually works much more smooth that way for some reason.

You can change the destination, time, or date of your reservation. However, you will have to pay an exchange fee and the difference in fare.

Here is the link to Tokyo and other domestic office phone numbers:

http://www.jal.co.jp/en/information/dom/branch/#tokyo

Just say, "Eigo, onegai shimasu." (English, please.)