I have a compensation question. In my signed offer, I am guaranteed paid holidays but being on a 4×10 schedule, my company will not compensate me for holidays falling on my day off. Can they do this?

I work Tuesday through Friday. Compamy policy is that if a holiday falls on my usual day off, I will not get holiday pay. I am salaried and have a signed letter saying I get Memorial day, Labor day, etc., paid. What should I do?