HELP!! I Signed Myself Into Slavery Because Of Unemployment And Now I Can't Get Out

Please I urgently need the help of any legal practitioners. I really don't know what I've gotten my self into.... I finished NYSC last year and two months later I was interviewed for a job at an Indian owned Pharmaceutical company. After two months I was offered the job as a Medical representative. My self and all other successful applicants were given a one-week training before we were all dispatched to our different states.
Among the employment forms we were given to sign there was a SERVICE BOND form which states that "I am to work with the company for TWO YEARS or pay a sum of 250.000" I signed because of the employment situation in the country and to be honest I was desperate I couldn't afford
to be unemployed I had so many family pressures I was almost becoming depressed.
I am now on the job and my people I AM SEEING HELL!!! I work tirelessly my salary is less than 100k I spend a greater amount of it on transportation(Nature of the Job as a Medical Representative I Move from one place to the other) we were promised a car for mobility but this is almost 6months and absolutely nothing is being said about it. I am under the sun under the rain working. I hate complaining because I feel it is synonymous to being ungrateful but some days I can't take it I feel like quitting on the spot!
After I realised the service bond I signed I refused to sign the offer of employment letter (I still have it in my possession). Now I'm seeking a less stressful job because honestly this one is beginning to affect my health. How do I go about this SERVICE BOND please I really need help. I can't pay that 250k I can barely save up to 20k every month infact successfully saving 10k a month is a miracle! And I can't work for another 18 months I'm not sure I will survive. Please I need Your help!