cannot attend international orientation

<p>Hi. </p>

<p>I'm an admitted international student. I already have my F-1 visa and documents, but I'm about to undergo a medical procedure and I won't be able to fly till at least Monday 26. </p>

<p>I sent an email to isss five days ago and haven't got an answer, and I still have to solve a bureaucratic mess, that's why I ask here. </p>

<p>Is there any possibility I could arrive after orientation? If so, how should I proceed? At the embassy they told me I should simply request another I-20 or a letter of authorization.</p>