How do I get my property back from an ex?

My ex and I rented a storage unit several months ago in Colorado. She is the primary holder of the storage unit but my name was also on the paperwork so that i had access to it. I paid the bill every month. She has about $50 worth of stuff in the unit where as i have several thousand dollars of my personal property in there. Anyways, she has the key and refuses to give it to me. i went to the storage location and they cannot give me access to the unit because she took my name off the agreement. How can i get my property back?