@ Sajha keto, making myself clearer. They will have to pay your pending salary. There is no way they withhold your salary. That is illegal. An easy DOL case.

The issue of Non-compete is different. Possibly, you told the dh*** company that you have already quit the job and now you need your remaining salary. They should pay it. They will pay. Question is - do they know you are still working for the same client? Layers and layers of vendors would not make a difference if your non-compete clause explicitly mentions that you, as ABC's employee (dh*** company), is not allowed to work for the client introduced by ABC. Which may categorically forbid you to work for that client. Say, client is Bank of America, Vendor is IBM, sub-vendor Tamilnadu Enterprise, their sub-vendor Rama Naidu Company and then their sub-vendor (i.e., your employer) ABC. In court, their claim will be that, per your employment contract, ABC introduced both Bank of America and IBM to you. So, by working for Bank of America or IBM you violated their non-compete clause. Actually, if you go through the full fledged litigation process, courts might interpret your employment agreement based on what is written and the circumstantial evidence. So my interpretation may be wrong as well because I settled out of the court and did not had chance to see what the judge would decide. Point being, these are all costly process. I doubt dh*** company will go all in. But be on the side of caution.

Do you suspect that they might know you are still working for the same client / vendor?