With all promotional discounts offered by eBay, in the T&C's it states "this offer may be withdrawn at any time" (or words to that effect). So you should be treating offers as a bonus and not a given.

The CS crew have given you the excuse "We'll escalate this to the relevant department", that is simply an excuse to get you off the chat line - it's never going to happen due to the conditions I stated above where eBay, at it's discretion, can cancel the offer at any time.