Ex Agent want me to pay him the commission

What is the name of your state (only U.S. law)? phoenix Arizona

Today I recived the below E-mail..
Sam,

I have left you two messages today with no response. Therefore, please consider this written notice.

According to the Buyer - Broker Agreement that you signed, you were under contract with me to purchase a property from 8/16/09 through 12/16/09. The agreement was for 3% or less per the commission offered by the seller.

On August 24,2009, you purchased a home with American Realty Services agent, Lawrence J. Goldstein. Because of the above contract, you owe Century 21 All Star a fee of $1202.73.
If we do not receive payment within 5 days, we will take the next action which is described on page 2 of the contract, lines 62 - 72.

I will never sign this paper he calles a contract if I knew that I had to deal with him exclusively...
the other thing that there is nothing in the contract that says that I have to pay him the Commission... it says something about dispute resolutions that shall be submitted to the mediation of the local Relator asscociation..

Please help..
Sam

well, without reading the entire contract, it is impossible to suggest if you are liable or not but since you have stated there is an arbitration clause, I suggest you avail yourself of the opportunity to have the dispute arbitrated.