I honestly mean this in the nicest way possible but writing on here wont do anything, you need to go above those who will sort it and get eBay to fire downwards, having messages passed to the relevant team doesn't work, getting customer services to politely send a message to accounts doesn't work.

Get on Likened and find all the business account people you can and fire off messages highlighting everything until you get it sorted. Being nice is all good when eBay are being helpful but if they are sending debt collection emails you really need to change tact as they clearly arent working hard enough to fix it.