My question involves employment and labor law for the state of: MA

I work for a company where medical bills need to be collected. My job is to collect them. If I collect a certain amount above my quota I get a bonus. Bonuses are paid in tiers grouped by ranges above 100% 3 times per year:

100% - 105% I get $300
106% - 110% I get $700
111% - 115% I get $1000
115% and above i get $1500.

This bonus tiering is company wide I have documentation to prove it.

Last period I collected 115% of my quota. My immediate boss signed off on me meeting 115% of my quota and forwarded the bonus paperwork to the Vice President for him to sign off on it. He rejected the bonus saying and said that he decided to change the quota amount I was supposed to collect. He increased my quota by $75k and now the amount I collected only brings me to 103% of my quota.

Can quota's be changed arbitrarily like this?

I am extremely angry and was COUNTING on this money as I worked very hard to meet the 115% quota mark. This has happened to a lot of the workers at my company. The last person to question the issue has been fired.