Your lawyer is your legal representative and he or she owes a fiduciary duty to you. Among other things, your lawyer must consult you about all settlement offers and must listen to your opinion. While your lawyer may strongly advise you to accept a certain settlement, if you say no, ultimately your lawyer must respect your wishes. If he or she does not, then you may be able to sue him or her for legal malpractice.
Legal Malpractice
Professional malpractice occurs when a professional you are working with, like a lawyer or a doctor, breaches the standard of care that is owed to you. You will need to prove that this breach occurred in order to show that there has been legal malpractice. In this case, the breach of the standard of care is that your lawyer did not listen to your express request. Since any reasonably competent lawyer would know that he must listen to his client's directive, the fact that your lawyer ignored your wishes can be considered a breach of duty. This breach will subject your attorney to professional liability for legal malpractice.
The trick is going to be proving that you actually suffered damages based on this breach of duty. In other words, you need to prove you would have somehow gotten more money or a better deal if your lawyer hadn't disobeyed your wishes. Unfortunately, If your lawyer did something wrong but you didn't actually suffer any kind of loss on the basis of that error or breach, then there is nothing for you to recover for. Since it may be difficult to prove that you would have received a better settlement or a larger verdict if your lawyer had not approved the settlement, you may have a hard time winning your case.
Getting Help
If you believe you have been the victim of attorney malpractice, it is in your best interests to consult with a lawyer for help to find out if you may have a viable legal malpractice case for damages.