You are in Houston so your contract and your Realtor are bound by the rules of HAR. Not any other MLS.
HAR has different ways of removing your property from the market.
1) It Sales
2) It expires
3) It is withdrawn - The seller withdraws the property from sale. You may not sell the property during the term or the listing - This should be reserved for a change in circumstances.
4) hopefully not for you a forced change in ownership such as death or foreclosure.
5) Termination - here your form will state if your are released from paying the Broker a fee or if you or to pay a fee when you sell under the period of the contract.
Now if you sold or are selling the property to someone that viewed the property while listed the listing agreement will state what protection period the Broker request. That period starts the day of proper termination or expiration and if you sell in the 30,90 ,180 or what ever amount of days are listed you owe a fee.
I hope this clears it up for you.
Be careful and read your listing agreement carefully...
Hope this helps!
DISCLAIMER: You might not have to pay amendment signed by all parties released you for any realtors fees owed.
Texas like many other states in US have laws a seller must follow in order to sale any property. If these laws are not followed you could be sued. Why many sellers have agents represent them therefore under e & o insurance for protection.
GOOD LUCK: Great you located a buyer !