Miscellaneous

My close friend is part of a reputed organisation for many years now and he travelled to us in work visa. He was still an Indian employee and was getting Indian salary and lodging in USA. For meals the company provided him an actual expenses per diem limit which is around 85 USD, for which the employee has to provide receipts to get the amount reimbursed.
When my friend applied for reimbursement, the employer is suggesting that he cannot eat anything beyond 20 USD per day. The employer also stated what he has to eat(like one food, one juice, one sides etc..). Also, they asked my friend to pay from his salary for meals which are more than 20 USD per day. But his allowance for a day is 85.

When asked why, the company claims that he bought more food than expected and terminated.

For his total stay of around 200 days, he had limit of 200*85 = 17000 USD.
But all he spent during the period was 30*200 = 6000 USD.

So in terms of savings, my friend saved around 11k USD for the company.
But the company has terminated him saying he should have spent only 4000 USD or lesser than that.

Can my friend contact USCIS and complaint against the employer?
I am GC holder in US and can I file a complaint on behalf of my friend?

Expecting some quick responses immihelp members.
Thanking in advance.