Please deposit all the checks in the bank and let it Bounce due to insufficient fund due to insufficient find reason again deposit all the checks including the previous check which was bounced earlier and get them bounced again.
Now you send the a legal notice for the amount outstanding, interest there on, loss of profit due to non payment and legal charges for sending notice say 10,000/- with information to pay with in 15 days in a given bank account failing which they will be liable for litigation expenses relating to this case.
138 case takes time but the 2 times penalty along with the imprisonment is there and this should not be taken as easy.
If it takes more than usual in civil court you may file a writ in this regard in HIGH COURT for quick decision.