Any payments you make are sent to a P.O. box (or, a lockbox), which is controlled by a different federal contractor. This
contractor sends files with your payment information to MOHELA for processing.
More specifically, you might ask, where do the funds actually go?
The payments you make (essentially, the funds making up those payments), including those made towards origination fees, interest,
and principal go to the U.S. Department of Education, not to MOHELA. MOHELA does not retain any portion of your loan payments.
We're here solely to help you manage your federal student loan repayment. Thus, the federal government is the recipient of those funds.
(Although refund requests are initiated through MOHELA, the refunds ultimately come from the federal government.)