Apartment complex water billing

My apartment complex uses con service to bill for water. According to my lease, they bill us for the number of people we have in the apartment. We had to get a cosigner, my boyfriends mom, and I’m worried that they’re charging us like there’s three people living in my apartment when there’s only two. Is there any legal way that I can deal with this. I feel like if I go to the apartment complex, they’re just going to tell me that because she’s on the lease, they can charge us for three people and it’s bullshit. She’s never even been to our apartment.