Contract Bond Query

I joined my previous employer through an upskilling institute. They offered me a permanent job based on my performance. After acceptance, they send me a bond for 1 year and they had not notified me about this during the initial discussion. I signed it out of respect but they did not acknowledge it from their end. After 3 months, due to greater project demands and long working hours, I decided to talk with them for a raise. I also had an offer in hand. The HR did not co-operate on this and I ultimately had to resign. I told them on mail as well as phone that my new employer is ready to pay bond if you provide me a signed copy along with letterhead of the company. They refused to do so and due to this, full and final settlement is stuck. The company's behavior is not co-operative when I tried talking with them. What should I do? I also want to check whether the bond is valid or not.