Service matter

Sir I am a law graduate, I worked as a retainer in a firm a on the basis of a Retainership Agreement made & executes between me and the firm, but sir at the time of taking \ collecting the cheque of my payment, the firm told me to sign of the Salary register of it. I initially refused to sign on that as I was appointed as a retainer but they told me to sign on it in order to collect the cheque and said this is the rule of this firm to give cheques and also told me if I have any problem later on for putting my signature on the Salary register, the firm will remove\delete my name from it, so that I do not have any problem. But after 6 six months the firm suddenly inform me, as it is no longer interested to work with me, and told me collect my last payment. Then I went to collect my payment, they gave me the cheque and that time I oppose to sign on the salary register and so the firm gave me a voucher to put my signature over it and leave the firm, I had done that but several times told them to remove my earlier signatures from the salary register, but Sir the Firm highly mis-behaved with me and told me to go out, and said that the firm will remove my signature\my names when it will think appropriate. And now suggest me please, whether I should give a termination letter to the firm by mentioning in it to remove my earlier signatures & my names from the register and ask fro their reply within a specified period???