On what legal grounds are they asking you to pay them money? Did you sign a bond or something similar on joining? I have heard anecdata of that not being enforceable.
Company HR will ask you to sign a bond once you get selected in the visa lottery. We have to sign this bond if we want them to go ahead with our H1B process. This is different from the bond they have for freshers (which usually lasts for 2 years at the start of your career).
Once we sign this bond, we have to accept whatever salary they offer for our onsite assignment (deputation to US). People won't even know their US salary until 1 or 2 days before travel. Then come to US and work for them for the bond period doing whatever they tell us to do. If we were to quit during this time for another job in US, HR can treat us as "absconding" and refuse to give the service letter unless we either pay the bond amount or come back to India and serve whatever notice period is on the bond.
>> People won't even know their US salary until 1 or 2 days before travel
That is messed up. Why is that "service letter" that valuable?
On a side note, as an H1B holder, I am really happy with a current administration's crackdown on work visa abuse. Companies like yours seriously need to be dealt with.
I don't know about India, but in UK if you have a notice period on your contract and leave before it's served, then the company can totally sue you for the work you promised you would do and didn't. So yes, a company can totally say "you can leave right now without working your notice period, but you need to pay us the equivalent of your salary for that time". Or they can say you can't leave until you worked the last day of the notice period - it's their right and something you have agreed to in the contract.