1 month's rent is not out of the norm btw. Actually if you offer less than 50% of a month's rent, it is probably not worth it to any agent to show especially with the prices of gas climbing.
The paragraph on Commissions, 5 of TAR-1102, covers the fees you should pay. Unless there is an entry under Other Fees, your liability is shown as the checked box 5A(1), (2) or (3). If (1) is checked and 50% filled in, that amount is intended to cover all brokers and all agents, including all their splits. Note that on the broker splits are disclosed under paragraph 8.
It's possible something is also present under 5D, but this is rare.
Be sure to check Special Provisions paragraph 15 for modifications that might change the commission owed.
Lastly, it is possible that your Realtor did not use the association's form, in which case you'll have to dig into it to find your liability for fees. A quick call to the broker will clarify for you and the Realtor what should be paid.
You may owe the commission to both agents. Check your listing agreement. This is common practice. By the efforts of your realtor the co-operating broker has brought you a tenant. While you could attempt to renegotiate the commission, your realtor may have advertised that on the MLS and would be obligated to pay the commission. It is not fair to either agent to withdraw your offer of compensation after the fact.
Look at your representation agreement and your leasing agreement and see what you signed and agreed to pay. If you are an auditory person, you may be remembering what you think you heard. It could be a simple misunderstanding. What is written and signed off on is what you agreed to.
I'm sorry about your problem. Have the listing agent go back over the listing agreement with you. Fees are negoitable, but they typically range from 50% to 100% of one months rent to the broker for leasing. The fee is then typically split 50/50 between the agents if more than one agent was involved, but it doesn't have to be this way. It just depends on what was agreed to in your listing agreeement with the broker. Good luck.
You need to read your contract. I do not practice real estate in Texas.
Normally the terms of commission payment are stipulated very clearly.
In California a lease commission rate is typically a set percentage of one years' rent, for example if the apartment rented for $1000 per month, it would be a set percentage of $12,000, split equally between the two parties.