I would get on the phone with someone and tell them (don't ask) in a nice way that you need flights closer to the time you booked because you have engagements that need to meet (ex. a wedding the night of arrival and go back to work at 8 pm the night of return home). so unless they want to pay for your rented wedding attire and the limo you paid for, and wages for missing time off work, those flights need to be closer to the times you originally booked.

I'm sure someone else will come up with better ideas, but that's where I'd start.