Changing College Decision

I was torn between two colleges and ultimately chose one narrowly over the other. I am now doubting that decision… Since I am doing a gap year now, do you think it would be possible to contact the college (Harvard) and reverse the decision? I mean, they haven’t exactly filled their class of '24 yet. Does anyone have any experience at all with this or know if it is possible? If so, should I e-mail or call my AO? I haven’t decided that I actually want to go through with it, but am very curious to know if it is an option. Any thoughts?