"Buyer" is not making payment to "Service provider" even after Payment

"Buyer" (NSE listed Ltd. Company) is not making payment to "Service provider" (MSME registered Pvt. Ltd. Company), even after receiving Payments from "main Client", for the Services delivered by Service provider. Main Client (Govt.) appointed Buyer (Consultant) and Buyer appointed Service Provider (Sub-Consultant) for part work. Service provider delivered the Services on time and the delivered Services and respective Invoices (submitted through Buyer) to main Client were accepted and Payments were done by main Client to Buyer. Therefore Service provider submitted their Bills to Buyer, which were initially acknowledged by Buyer and minor Part payments done as well. But now after few months of accepting the Invoices and making minor Part payments, Buyer refused to make balance payments and terminated the Contract in the name of Behaviour, Quality Checking, Inferior Services, Soft copy submissions (taking favorable interpretations of secondary Contract clause to escape from their lia