How to write a increment letter?

Dear sir,

I employed in my company as a claim processor with salary 1700 plus 0.25 halala for one claim(after 2500 claims,they are calculating per one claim 0.25 halala,2500 claims are our target) in the last year i got promotion as a claims supervisor but so far i didn't get any increment at the same time i lost my overtime.now my family also with me,son has study in 2nd.so i want to give a letter for salary or let me find another job(should provide my release,when i get job)so please help me to write a good letter

yours sincerely

anwar