Contracts and exploitations (Manama)

Hello everyone, please i need help and advice. I have been in Bahrain for 7 months now, working under a security company in Bahrain.Before coming to Bahrain i received an employment letter with basic salary of 140BD which i signed and sent back to the operating manager for my visa to be issued. all these was through our agent in Bahrain and the former operating manager of the company working together. Now the operating manager is out of the company and the owner of the company and the new operating manager are saying that the contract was not correct. that the company pays workers 100bd as basic salary for all their employees and 25 bd as salary for 4 hours over time. They say all workers work on 12hours earning 125bd as salary.
After a quarrel with them, i told them if they say they pay 100bd for 8hours duty, then 4 hours duty should be 50bd as overtime giving as total 150bd for a 12hour duty. please i need help and advice because i am working presently for 8 hours and earning 100bd only which cant do anything for me and my family back home since i denied the 25bd as money for 4 hours overtime.i have copies of the contract i signed with them, one for 100bd and another for 40bd, making all together 140bd as the old operating manager confirmed to us through a mail he sent to us. Now they say the contract for 40bd was paper work for visa purposes at LMRA which i dont understand. I spent 500bd for visa and 500bd for my airticket to bahrain and now the salary from the company will not help me. I do not want to go back home now because the company owner said if we dont agree, i should pay my airticket back home and come to him and collect my passport. i dont want the company anymore and want them to release me go to another company since they dont want to pay me the salary we signed in our contract.
The worst issue in the contract is that, they say if i want to leave i will pay 700bd to the company and pay my airticket back home.our leaving condition is crazy, all toilets damage and they dont care. I have 1 year 5 months left for my contract and thinking never to come back to Bahrain with all these experiences.Same thing happening to 2 of my friends we came together through the same contract. Waiting to here from you.
Thanks.