Pension to Bank Officer

I had opted 'irrevocably and finally' for Pension in lieu of contributory PF, June 1994 when asked by employer after signing Industry Level Bipartite Agmt between IBA & Employees of Banks. Due to legal formalities and adoption of Pension Rules by respective banks on the lines of agmt, the scheme was notified in 1996 and implemented in 1998 with retrospective effect from 1/11/1993. In Dec.94, I left the services of the bank asking for relieving under Voluntary Retirement Scheme with Pension, as per said option. Since the Pension Rule was not passed by the Board and notified, I was asked to resign and receive PF which could be refunded when the Pension comes into effect and refund PF with 6% interest. My request to do so is denied, saying that the scheme was not in force. It is total injustice. Can you advise with some case laws on Pension and Contractual obligation?