Non payment of dues

Hi, We are very new and small company. I had a client to whom we have provided a manpower resource on a fixed monthly pay. Right from starting client has been taking us for granted and always delaying the payment. Client's attitude has been totally unprofessional during our engagement when it comes towards payment. This has severely impacted us we are not with deep pockets to pay resource salary without getting payment from client. This has seriously impacted our reputation in eyes of our employee. In March 2019, suddenly client came and started blaming us that our resource is not capable to handle the work given to him. When inquired, we came to know that client has given work to our employee on skills for which client has not hired our employee. When we discussed with client then he asked us to terminate the contract in march 2019. As per our initial agreement, client was supposed to give us a notice of 2 months for terminating the contract. However because of client's unprofessional attitude we had to terminate the contract as he was already holding our payment for two months. From last two months, we are chasing for our payment but client has refused to make the payment to us mentioning that our resource didn't completed the task given to him and hence he can't make the payment until and unless we as a company don't complete his work. We have been very clear with client that our responsibility was to provide a resource. Since he has already used the resource till March, so he need to release the payment for resource. There was no back to back understanding of delivering his tasks after terminating the resource contract. He has been totally unprofessional and always make us fall in his mesh before making the payment. But this time we don't want to act as he want. We want to be professional and want to teach our client a lesson that he can not take us for granted and want our full payment to be released asap. I am looking forward for a legal advice on how to go ahead to handle this scenario. Regards,