Coal India limited

I joined in coal India on 3rd April 2013. I have singed 3 lacs bond for five year. As per bond agreement Coal India will deduct rs 5000/- pm from my salary to secure the bond after five year they will refund with interest. I applied Indian cost account service through proper channel and get selected. I obtained NOC. I gave 3 month notice. But they process my resignation in delay.i gave notice in August 2016 and he write letter in December 2016 to Director of Indian cost service for transfer of bond. They intimate to Coal India that they will get approval from ministry and request for relising me for the joining. But the officer of coal India did not consider this letter and ask me to deposit the remaining amount of Rs. 75000/- to secure the bond and also said that if bond will transfer then you will get full amount of RS. 300000/-. In April 2017 ministry convey the approval to transfer of bond. And Coal India officer write a letter for acceptance of the transfer of bond to higher authority and copy of the letter is given to me. But after completing the 5 year they deniying to refund the bond amount and said that you have deposited the remaining bond amount hence bond amount is not refunded