Horrible service from the store manager

I was at truworths in sandton to exchange a skirt that my mom bought for on 3.05.2010 and the skirt was bought with my mom's account . I wanted to exchange for the same thing just a different size the manager came and told me that I can not exchange it till I get the account holders card ,I'd and my I'd I should also bring the letter of authority than the manager asked one of the sales consultants to call customer service and tell them that she told me that I can't exchange she than want at the back to do banking left me there standing for a good 2hours i than asked the sales consultant to please call her manager for me, the lady came back told me that her manager told her to tell me that she can't be running up end down for because there is nothing she can help me .. y is it a mission to exchange just for a bigger size I have the slip with me and the tag is still attached ( item still in a resealable condition ) but no one was able to help me instead they gave me a horrible service .....