First of all submit the claim of Bills and payables by company to you under proper acknowledgment and narrate the representations made till date and mention dated, names/designation/name of company/address etc.......................
Thereafter in gentle manner narrate the amounts offered as payment against actual amount..................and request to pay in full.
Record the transactions (audio/visual) during which the less amount is offered as precondition and as ‘If at all you want to be paid’ and thus keep some evidence of blackmail, intimidation, coercion etc..............
If a FNF receipt is extracted by force withdraw it immediately in writing under acknowledgment you come out of office.
The onus is on you.
If possible keep some unshakeable witness (es).
The evidence shall help you in all forums.