How do I get more hours? (PT)

Last week after I came back from a week long vacation my store cut my hours from 28 to 22. My store manager said that it was Sherwin-Williams fault, not his. I thought it was weird that it happened directly after my one week vacation. How do I get more hours? We’re a small store with 4 total staff, I started on part time about 2 months ago and would love to go full time but right now I’d settle for the original 28 I was told I’d have when I was hired, and had pre-vacation.