Where or how to make a cheer skirt bigger at the waist?

My cheer skirt was made too small for me at the waist and I have a pretty big hip. Since it's too tight, it makes it so much shorter. I have two skirts; a pleated one since I'm in varsity, a flyaway - I don't want to waste around $300 buying 2 new skirts especially when I got it not even a year ago. Is there a place to get it altered at or can we send it back to where it was made? It is from the company Varsity. I don't want to ruin the skirt by making changes myself but our rally is coming in less than a month and I feel claustrophobic in it so I will if I have to. Please help! (So sorry for being really descriptive!) Thank you so much!!