Payment default by customer - How to recover

We supplied the accused party, (a Food trading company) with processed food orders around time of August 2014, they owed us total of Rs 6 lakh plus since then. They have owed us Rs 1.845 Lakh since March of 2015. In April 2015, we reached agreement on a payback schedule to be paid back in full by first week of August. They have since only paid Rs 20k. I did agree to them that would give them an 8% profit margin .. meaning that the amount outstanding now should be Rs 149,740. However, he has used up our goodwill. The interest alone that he could have made on our money by putting it in a money market account is equal to that profit margin that we had agreed to. And that is not including that it took them almost 6 months to make payments on our original bill and one of their original checks bounced and we had to pay a fee on it. We would like to call for Rs 1.6 lakh at least with any more delays.