Should I give collection agency my account info to payoff a debt?

I want to settle with a collection agency for a bill that I owe. I have 9 days for the payment to be made. I offered to send a money order today (7-17-09) but they said that it would not be processed by 7-29-09. They say that it can only be done with checking info over the phone. Now, I'm worried about them having my info and even taking the whole amount owed instead of the settlement amount. Is that possible?? Is there any other way I can send the payment without being screwed?? Certified Mail maybe????? Please help!! - Is this your question? Add additional information