Collection agencies will contact you by phone and by mail, repeatedly if necessary, to try and get you to pay what you owe. There are laws regulating what kind of contract is allowed. Once the debt is at the collection agency, you must deal with the agency. It is usually too late to make a deal with the merchant. Most collection agencies want the full amount now.
If they agreed to installments, it will almost always be three or four large ones. Sometimes they may be willing to settle for less than the full amount if you can pay the entire settlement at once. Be sure to get such an agreement in writing and let a lawyer look over it.
Do not let a collector keep you on the phone wasting both your time in his or hers. If you can't pay, say so impolitely hang up. For further information on what collectors can do and can't do consult with a lawyer.
Special notice: If you have any doubts about the actions of a creditor, contact the Texas Attorney General's Office for Consumer Affairs.