What state are you in? As for the fees, you never pay just what you borrowed. They are charging you a HUGE finance/interest charge. If you want to pay the loan back, you have to pay the principal + the finance charge. If you made any payments at all before defaulting, they were just finance charges and the loan was rolled over.
It is most likely that the payday lender you have your loan with is not licensed in your state. Was it an internet payday loan, or did you go into a storefront to borrow? Storefronts almost always follow state laws and can garnish your wages if it is legally allowable in your state.
If this is just an internet payday loan, send them a letter via certified mail/return receipt requested, revoking any voluntary wage assignment you may have agreed to when you took the loan out, and also send a similar letter to your payroll dept., stating the same. They should not honor the garnishment request from the payday lender if it is not court ordered.