You can do the following steps:
1) Issue a legal notice to the company to pay your outstanding dues.
2) Also request the company not to use your name on the website as you are no longer working for the organisation.
3) If the company fails to do so file suit against company to recover your dues and injunction restraining company from using your name on their website.
There is no defamation committed by the company. The remedy for you is to file a lawsuit for recovery to recover the arrears of your salary and a separate lawsuit for injunction to restrain the company from using your name on the website.
You first issue legal notice to the company instructing them to refrain themselves from using your name anymore in any aspect and for anything especially when you have already disassociated yourself from the company ever since you have resigned the post. You can warn them of strict legal action if they are found to continue with this illegal action harming your reputation and personal liberty and rights. Subsequently you may proceed against them legally as per the provisions of law for the purpose