should i be entitled to retro pay

I started a job just under two years ago and was told I was going to make 12 dollars an hour contingent on completing all trainings, and 11.50 an hour until the trainings were completed. all trainings were supposed to be completed within 90 days of employment. the company gave me all but one of the trainings before sending my into the field to work. I have been waiting and asking periodically for the training for just under 2 years, and have only been making 11.50 per hour worked. when I get my last training are they required to pay me the .50 per hour worked while waiting for them to schedule me for the last training?