i have been making payments to pay off what i owe and i have made 2 payments out of 4, and i ran into some car trouble and can't make this months payment, am i within my rights to tell them to skip this one and should they be able to do it?
Eric,
Sara sounds like a debt collector for a bottom feeder agency. You are clearly doing the right thing accountability for you debts. As you are paying them they will treat you like a customer now. Call them up and explain your situation and if you get bark from a associate you need to talk to a manager. Make it clear you are making every effort to pay this however I need to fix my car so i can make it to work to continue my agreed payment to you.
So you defaulted on a debt and it ended up with a collection agency. The collection agency gave you a second chance and set up a payment plan. Now you want to default on that payment plan?

If you miss or are late with your payment to the collection agency, you will have voided your agreement and they will come after you. Make the payment as you arranged and take public transportation for a while.
the bottom line to the debt collector is he or she has heard it all.
you are paying for something that you bought or ate or whatever, it is in the past and you really are not concerned about it. not as concerned as something you need now, like your car repaired.

from what i get from your question is you have already missed two payments (2 out of 4) doubt if they have that much confidence in you making regular payments.

if there was a judgment made against you and this is what you are paying, then you can't just blow it off,
call them and see if you can pay a least of portion of what they expect, you might not think this is much of a big deal now, but 5 years from now when you want to buy something and your credit is in the toilet it will mean something then.

good luck
If you are paying a collection agency, then call the collector and explain your situation. Unless you gave them direct access to your bank account, there is nothing that they can do.

If you can not afford it this month, then you can not afford it.
Anytime you get in that position, you're ahead to call the collector, or who you owe. They'd rather work with you, than think you just avoided it, or forgot.