Recommendations on negotiating invoice discount with a warehouse that mismanaged our goods for a year?

Like the title says, we shipped goods to warehouse based in the US and they mismanaged our goods for a year (could not confirm inventory arrived, multiple months misplaced inventory, one month+ to ship inventory, hundreds of emails asking for status update and pushing to complete work orders).In the end they cost us a lot of time and money dealing with their mismanagement. Thousands in extra shipping fees and missing Christmas selling season entirely and hundreds of missing units.Today we received a full invoice as if they had completed the work without error or delay.We obviously are obligated to pay some amount for these services even if the mismanagement cost us significant extra time and money, but we think it should be significantly discounted.Any recommendations on negotiating a discount on invoice for grossly incomplete/delayed services? see hubwealthy.com/wealthy