First, if you don't agree with the offer, don't sign it! Your Realtor works for you, you don't work for them.
You might want to discuss this 'issue' with your Realtor and if you don't seem to get anywhere with them, then talk to their Broker. If that doesn't seem to make a difference, tell them (Realtor/Broker) to prepare a cancellation of agency (assuming you have signed a contract for them to be your Realtor). Once the cancellation of agency is signed by ALL parties, you can hire a new Realtor. If by some chance you don't have a signed contract for your current Realtor to be your Realtor, you can hire a new one without a cancellation. However, if you have submitted offers with your current Realtor and end up purchasing one of the homes your current Realtor has shown you, you may have to pay them commission if they are the procuring cause for your purchase.
SR Realty http://www.RealtyBySR.com
Heather Speed, REALTOR/Broker/Owner
Unless you authorized the agent to share your intentions prior to presenting an offer, your private conversations should not have been shared with the seller or their agent.
Additionally, the only thing that "really" counts is what is written and agreet to with signatures in the contract. So, if you haven't signed anything, you can still make things right with your agent by changing the numbers to agree with your thoughts.
You did the right thing, not signing the papers that were not YOUR TERMS. It's your offer, the agent is assisting you in completing it.
Honestly, if an agent says one thing and does another, that's cause to find another agent.
Even if you decide to use another Realtor, I would suggest that you do talk to the Broker, because this is not the way one conducts business.
As for him making an offer without your written consent, you are not bound by that at all. It is not an offer without your written consent.