A woman goes to clothing stores, selects the items she wants, and then changes the price tag placed on the items by the store to another price, such as replacing a price tag for an item priced at (10) dinars with one that says (5) dinars. She then buys the item based on the price she altered, which is less than its actual price, claiming that the store will change the prices after a month. She believes she is not acting improperly and that her action is not forbidden. What is the ruling on this?