Call/do an online chat with the Embassy department in the country you are located, if possible. But they weren't terribly useful to me. E-mailing directly with that department, or doing a Skype audio call is an option. E-mail tends to work best here as the staff is typically not all that... let's say, patient.
They told me I could postpone the interview for up to a year after the last action, which means I have until around mid/early next year.
I likely will be going through the process sometime between Jan and March.
Best of luck. As with anything from a random stranger on the Internet, YMMV and you should definitely talk directly with someone at the Embassy that handles these issues.
Jdtravails got a reaction from TBoneTX in Wish to Postpone interview/initial Visa approval