Boots that I was told no one had

On Tuesday, 14th July I went to Waterfront store as I knew they had a sale. Saw a boot that I wanted and went back on the Thursday to be told from different staff members that it was sold out and I should have asked them to set aside (I was always under the impression that sale goods could not be set aside). I then asked the sales assistant to check if Cavendish has the boots, I was then informed that they dont have my size in stock (a UK/SA size 6). Today I called Cavendish, only to find out they suddenly have a pair, but the promotion is over (the extra 30%). I then escalated to operations manager at headoffice, called Catherine. She then dealt with the matter only to eventualy inform me that they \sorry"and cannot give the boots at the discount"