Bad service from area manager

I recieve a gift in Jan summer clothes from the truworths store and now when I want to exchange for a bigger size they are refusing as it has passed their one month return policy. But I fail to understand why because I'm not returning I'm exchanging and when I called head office they say the area manager will be able assist when I ask for the area manager she said she cant help me. This is the truworths store in dobsonville. I am very disappointed as the items are still new with price tags.