Try this,
Write an open letter to the Manager of the store, the CEO's of the Companies involved and send it to the local and national papers for the area, in the letter explain the situation completely factually, no embellishments, and express your disappointment that as a result of what they asked you to do, you will no longer be able to buy from the shop and that you will no longer buy the brand because they condone the practice by not stopping it.
You may get nothing, but what you will have is the satisfaction of making the issue public, others will see the letter and may have similar stories to tell which is never good for the shop/brand.
Put shop employees names (if you know them) as Mr X or Ms X as you are explaining the situation that exists not having a pop at individuals.
The key to the letter is simply to ask the shop to explain its practices by replying to the letter, it is unlikely that they will want to do this as they cannot justify their actions so you may get a resolution that you want.
You could also re-visit the shop, speak to the manager if possible explain the situation and that you intend to go public if you do not get the watch that you asked for and that had been promised to you by X without any pre-conditions.
If you are polite and courteous during the conversation this will help when the letter is written, difficult to get a response if you have told the staff to Foxtrot Oscar and stormed out.
I have used this twice, once with a restaurant and once with a travel company on both occasions I received a grovelling apology and some restitution when I revisited.
Have a go you have nothing to lose.