How to recover money from trainees after on-credit training?

Dear Sir/Madam, I run a computer training institute and i had given computer training to some candidates through a training partner under STAR Scheme of Govt. of India in 2014. The training was on-credit and no fees had been taken by the candidates. The assessment fees(1000/- per candidate) was also not taken from them and paid by our training institute. Before training, an undertaking had been signed by each candidate for the purpose that when he/she receives the reward from Govt. in his/her account, the course fees(9000/-per candidate as decided by the training partner) will be debited from their account and credited to training partner's account. But when i submitted the undertaking in bank branch, the bank authority informed me that the candidates had withdrawal the total amount (10000/-per candidate) from their account through ATM before submission of undertaking in bank. I contacted the candidates and tried to explain the whole procedure, but they are not ready to deposit the amount. They are saying that the amount is their scholarship. I tried by many ways but failed. Now, what to do? How to recover fees from them? I have with me one original copy of undertakings signed by each of them. Please refer to the website for details of the STAR scheme:- Thanks in advance.