How to recover for loss/theft of items when apartment complex admitted fault/liability?

Poor record keeping caused our storage unit that we pay additional for to be emptied. They thought it belonged to a different apartment that just moved out. Half of our items were returned, some of our items they claim were trash and "threw away", and then there are items that they are now trying to say weren't there (although, to begin with they didn't know where our stuff was, and where it went). They offered us $466 but when I refused they offer and said I wanted to be reimbursed for all missing items they are now dragging their feet on a decision and are trying to tell us we need to file the claim through our renters insurance and not theirs.