Cancellation of listing agreement

[Sara Underwood]

Hi
I'm a seller and have decided that I want to cancel a shortsale after waiting for 6 months and hasn't got approval from the bank. Both buyer and I have signed the "Cancellation of contract, release of deposit and joint escrow instruction" form and the buyer got their deposit back already.
The agent initially changed the mls status to withdraw. I have followed up several times and finally he agreed and has changed the mls status to cancel. At the same time I also ask for a cancellation of listing agreement form from the agent and it has been about 3 days since he changed the mls status and I've got no response from the agent.
Is my listing officially cancel? Can the agent come back later on and ask for any cancellation fee, or his commission if I decide to sell my property at a later time? Can he arbitrary change the mls status back to withdraw?
Can you please advise what to do in this situation in order to get the listing agreement cancelled officially? Thank you.