A Buyers Brokerage Agreement is a binding agreement until the term expires and/or the agreement is released by BOTH parties. This agreement is intended to create a mutual benefit for both the Agent and the Buyer and is enforceable in GA by law.
Why do you want to cancel the agreement? If it is because the Agent is not providing you with acceptable service, I would recommend you tell them and allow them to improved their level of service to you. If they continue not to provide you with good service, your next step is to speak with their Broker.
If the Agent has provided you with good service and you have now chosen to make an offer on real estate without them, you can do that, but you WOULD be obligated to compensate the Agent for that transaction as specified in the Buyers Brokerage Agreement.