Company Refuses To Upgrade Me To Full Employee Status

House am confused l don't no what to do, am an analyst on one multi national company do l work there as casual staff, and they is a staff who was employed to do the job but simply because he doesn't no the job l became the best for them now the staff have been redeploy to another department and promising of my appoitment letter for over 5 months, now the new employed manager does not nothing in respect to the job, l does everything, but now am getting tiried of the job, they are paying well first, and l close late every day, work from sunday to sunday. Please l need somebody to help for a new job and advice.

Yea, I'm kind of curious too 

Thanks very much for the offer