[Il] - denied my 15 year PTO bonus

In Illinois

I've been at my job since 2009. they implemented at 15,20,25.... years of service you get an extra chunk of PTO, kinda like a bonus. when I hit 15 years, they said no, bc my benefits date was 1.5 years later. I was denied several things when I was at 10 years even bc of this. that 15 year benefits date just came for my 15 year benefits date. they said did an audit, put my date back to 2009 , and they still won't give me my pto bonus

legal? they said i can have a phone call and I haven't done that yet. I'm not sure what to say or how to proceed. my supervisor got involved and i am still being denied. I debated a lawyer but, $$$

I started in 2009 and the date they said they use that they can't change was in 2011, and it was changed.