How to change the lawyer in middle of the proceedings

1. How to change the lawyer? (when I said my advocate that I'm going to see someone other for proceedings, he said he will dismiss the case)

Ans : Old lawyer does not appear in case which has been taken from him. He is nobody to dismiss your case.  He can share weaknesses of your case with opposite party which will be a professional misconduct which can bring him on road but not easy to prove.

2. Secondly, How long the Tribunal can provide the time for filing the rejoinder?

Ans : It appears Tribunal has given suffcient time.  Have you paid lawyer as promised?

3.What is the procedure if advocate refuse to provide NOC to appoint some other advocate?

Ans : New lawyer will tell you.

either way the new  lawyer will charge full fee for the entire case and take no respensibility of errors (which he can assume) of  previous lawyer.

You have the right to get you case represented before the appropriate Forum. Send under the covering letter the vakalatnama duly signed by you and your new lawyer for NOC. If your previous lawyer is refusing to sign/give NOC, you have an alternate to make an application before the FORUM to remove your present lawyer giving the entire details. As per my understanding of the law, the FORUM will follow the principle of natural justice. Let your new lawyer keep the Rejoinder ready to be filed before the FORUM.