hourly (raises) increases

[treloss]

i live in ohio. i am reviewed and my hourly rate increased bi annually. in november i was reveiwed and increased but was told i would not get the increase until april 1 (due to a "new system" going into place)i was assured that the raise would be retro. now they are saying my previous raise raise is built into my most current raise. i know they owe me for the months i was without the increase. am i right?
how would i recover this money without getting fired?