Nyc Employer Is Paying Me Less Than The $17/hour Stated In My Contract And Says It’s Because Of A Union Probation Period. Is This Legal?

I'm 20 years old I’ve been working at my job for about 3 weeks. When I was hired, I signed a contract stating that my pay is $17 per hour.

I normally work from 8 AM to 4 PM, but my boss recently asked me to stay until 6 PM to take out the garbage because that is the time it needs to be done to avoid a city violation/fine.

The problem is that since my first week, I’ve only been receiving about $400 per week, instead of roughly $500 per week based on my regular hours and the $17/hour rate.

My first payment was by check, but all the payments after that have been cash.

Today my boss told me that the position I’m filling is a union position and that I’m currently on a 3-month probationary period. She said that after the 3 months I will start getting the rest of the money. She also said that right now I’m being paid as if I were covering someone’s vacation.

The thing is, I am not in the union. I have not signed any union membership paperwork or any union agreement. Nobody explained to me before I started that my pay would be different during a probationary period.

I’m confused because the contract I signed clearly says $17/hour.

I’m in NYC and I don’t know what my rights are or what I should say to my boss. Should I ask for a copy of the union contract or collective bargaining agreement that supposedly applies to my position? Should I ask them to explain my actual pay rate in writing?

Is this normal for a union position during a probationary period, even if I’m not a union member and never signed anything? Or could my employer be underpaying me? What should I do? Location: New York (NYC)