It's a very big decision to make and just like you, it took me a long time to decide. I have mailed my declination forms and received calls from the respective SA admissions rep. It may be different for every SA but it may not hurt to give them a call before the deadline just in case the form...
Have you accepted the appointment and want to rescind or are you just deciding not to accept?
There's a form you have to sign and mail back to turn it down but if you never accepted, by tomorrow or after May 1st, it's a moot point. They'll assume you don't want to go. You may also call...