Hi Shaksham, I know it can be upsetting and I have been there many times. I hope it gets settled. Cost of doing business = things being delayed and I hope you had taken an advance or something.
As to what you would like to do if it isn’t, depends. Especially on how much money is at stake. And how much you are willing to fight / burn bridges, etc.
You’d probably need to approach a lawyer and check the validity of the contract and what you could possibly do. At the very least, you could probably send them a legal notice (costs a few thousand) and then worse case, file a court case. It will be a civil case which will take years.
If they are not paying you because they are not happy with the work, there is always arbitration (if it is there on the contract).
Keep in mind that Time = money
And, peace of mind is even more important.
I have been part of a team that has filed a case in India against another company (and won) — but if you ask me if it was worth it, sadly it wasn’t. Wouldn’t do it again unless my life depended on it.