Poor service

It was my first experience at the shop in Pavilion Durban. I came in looking for a long sleeve tshirt since I was going hiking. The lady sold me a spencer instead, costing R299 and she made me take a large. Why she never told me she was selling me underwear? I am livid to say the least. Worst thing is this thing is big and I am not allowed to exchange it. I hate poor service! People are chasing sales at our expense. I regret going into the shop yet I spent over R3500 that day since I also bought jackets as well.