Man... I think u need to see what is exactly written in your contract. It should say how much is ur actual working hours... Accordingly it should also say how much is lumpsum amount they would pay... The contract also should mention what is the overtime rate you should receive... What should be ur basic... Please read them first then speak to the HR. But if now the contract is not mentioning any of these things then this is a serious matter. Being outsiders we don't have much previlege to fight against the company. But the fight can be taken up before joining... Anyway please check whats there in your contract... Wish u all the luck...