Harvested my data and shared it around

I bought a pair of trousers and then exchanged them for a different size. In order to do the exchange I had to fill out all my details, including my ID number, email, etc. Why??? Why do you need my id number to swap a pair of pants? Since doing so I have been receiving marketing emails from Exact and sister companies Jet, Stern etc. The unsubscribe button don't work. Why did you force me to give you my data and then shared it around? I don't trust you at all and have no reason to return to your store or any of your related companies