My resignation is not accepted by the bank

I am working with a co-operative bank as Assistant branch manager. Me and my husband are working in same organization and I am on higher position than him. I am not feeling comfortable to continue working in same organization due to this issue. So i have submitted resignation with immediate effect and mentioned reason due to personal problem. It is mentioned in my appointment letter that - if you desire to leave Bank's service any time from joining the bank you will be required to give one month's notice to the bank or one month's pay in lieu thereof. According to this clause i am ready to pay one month's salary and i have informed the same to concerned authorities and maintained required amount in my salary account with the bank. I have personally conveyed my decision before submitting resignation letter to all concerned authorities. I have informed my decision is firm still the Bank has rejected my resignation. What can i do next as i don't want to continue my current job and i already have job offer from another organization.