Did I do something wrong?

[adpiucf]

No one can say for certain. But you may have taken too long to get back to them, or they viewed your reasonable request for time to consult your schedule as disinterest and filled their class with people they perceive as more eager. Many Greek organizations want to see really eager new members who will drop everything for them. Your request was not unreasonable because you emailed him the same night, but they're they ones with the keys to the kingdom and maybe you didn't come running fast enough or convey the high level of interest they wanted to see. This is all speculation.

Or perhaps they're simply trying to clear their schedules or to teach you a lesson in not keeping them waiting. Or they met someone they liked better. Or they haven't checked their emails and texts yet. It has only been a day; so maybe you're being a little melodramatic about them "hating" you.

Don't contact them again. Two times is ok. The third makes you a desperate stalker, especially because it has been less than 24 hours since you saw these guys.

Rushing is like dating. Sometimes someone loses interest and is too immature to tell you to your face, so they just ignore you until you get the hint and go away. And sometimes calling someone multiple times after you've only been out on a date with them once is considered creepy and overkill.

Better luck next time with the other fraternities at your school.