Non payment of balance amount

I am running my own solar business. before a month ago we had installed a solar water pump on our customer site. we send him the performa invoice and got signed by him which includes bill of material and work that would be performed by us. he gave us 50% as advance money to our company through cheque and after getting his work he is refusing to pay the balance amount by giving us the reason that i want this production of electricity to be banked to discom. which is not possible as consumer needs to take some approvals from discom before opting for banking facility of electricity and this could be only possible in case of AC connection while the system that we installed totally works on DC connection. He was cleared before opting this. but now he is making execuses and his simple intention is not to make payment. we have send him legal notice through our lawyer for which we didn't received any acknowledgment from him. now my lawyer is demanding a fee from me and want to file a case against him which i think will be a very long procedure. please suggest me what i should do so that my money can be recovered. can i simply file an FIR by visiting my local police station or i should go by court way. my lawyer has filed 420,406 & 126 case against him in legal notice.