Required advice for break of service agreement bond.

hello sir, i was working with a company in delhi as manager, at the time of joining they have suddenly asked to sign a bond and due to i had left job i have signed bond, it was one sided bond, after that company owner and senior person start mentally torcher. and due to some personal reason i had left company after six month, so now company send me notice to pay certain amont. they even not provide any training. so what should i do