You need to file a motion to revoke mediated settlement agreement and set a hearing so the Judge can hear the situation. Under the facts presented, this will probably be denied and a decree entered along the lines of the settlement. If the decree is already done, you have to file a motion for new trial within so many days, but again, it is highly unlikely to succeed. Unfortunately, it sounds like the hard truth was given to you late in the game, and you accepted it as stated by signing the agreement. You should have (and I know hindsight is 20/20) not signed the agreement and just gone to trial. Many times you end up worse than if you just settle, but at least you would have had your day in court.
This answer is intended for informational and educational purposes only and should not be considered legal advice nor forming the attorney client relationship. This attorney is licensed in Texas.
I think you may be a little careless in your phraseology. It doesn't sound like you were forced. It sounds like you were told some unpleasant facts by your attorney. Now, did they hang you out to dry, so to speak? Maybe. But, you weren't forced to agree to something. You could have refused to sign, fired the attorney, and retained new counsel. But, you didn't. Getting a settlement rescinded will be tough. What, exactly, are you looking to have changed?
This answer is not to be considered a response to a specific legal issue in a specific jurisdiction - it is to be considered only a general response to a hypothetical scenario posed by the questioner. For specific legal advice, please consult with a licensed attorney in your jurisdiction.
I would add that because the law strongly favors the enforceability of MSAs, you will essentially have to prove fraud, duress, or mental incapacity ito the court's satisfaction n order to have the MSA set aside. It is a difficult burden to meet.
The foregoing is offered for informational and educational purposes only. No attorney client relationship has been established and you should consult with an attorney to obtain specific legal advice.
Down here in this area, the mediated agreements are enforced, but under your situation, you may have grounds to request that it be set aside. You probably need a local attorney for this - and yes, trials are expensive so that was not a trick.
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