which dean should I email for this student problem?

Every University has a cut off date for receiving any sort of refund.

They're available and stated up front.

The fact they were allowing you to make partial payments instead of demanding full payment upfront doesn't somehow entitle you to not pay the contractual amount.  You signed a contract to pay X amount.

If you're trying to beg a way out of making those payments, the first step is to not try to do this by email.  Start by visiting your adviser, who might very well be able to help.

i would just write to the one in charge of your classes

You don't go to the dean of anything.  You need to talk with the finance or bursar's office.  This is a financial matter, not one about your academic ability, cheating, other student conduct, etc.

I agree with Drip, you really should have talk with your advisor and the finance office before withdrawing from classes.  You also have to look at the "contract."  Most universities require payment before the term starts.  Student may withdraw and get some or all of their money back in the first couple fo weeks.  After that time, it doesn't matter whether or not a student attends a class or any classes or even withdraws from the institution-- they student is still financially responsible for the fees.  

You may be able to work out a payment plan, but I don't think you should expect the university to simply erase your debt.  Good luck.

You should of gone direct to your college adviser. Before dropping any classes.   Go now ASAP. . 

You should get a meeting with the Dean of students. / enrollment.    Makes sure to have all documentation for the emergency.  You need to do this ASAP.  I don’t know if anything can be done if you dropped classes first. How long ago did this happen?  

Email the dean of enrollment; good luck!