I owed to Cingular Wireless and I set up 2 payments

I am assuming that you set up a check by phone for these dates. First of all, never set up post dated checks with a collection agency. THere is nothing stopping them from cashing both checks. You could possibly go to the bank and talk to the branch manager and see if they can reverse the charge.

Does your bank have over draft protection? If it does, then the transaction would have went thru fine, but if it didn't, then it would have bounced that transaction back to them if they had tried it. This has been done to me also. From my experience, the bank will not do anything to help you now, other than not let it happen again from that certain company. My bank used to always send out a form for me to sign that stated that so and so company could withdraw money from my account on a certain date. See if your bank will do that for you from now on.

There is plenty stopping collections agencies from cashing post dated checks before the agreed upon date. It is illegal.

They have to, by law, inform you via mail 3-5 business days before depositing your check into their bank. That gives you 48 hours to cancle said check if there are any problems.

If they do not send you a letter and they do deposit your check in their bank any time before I suggest you hire an attny.