Failing system problems are not customer problems

Failed to get assisted at The Mall of the South, Frasers Luggage a store I had been referred to by Frasers Clearwater Mall. As their system had reflected that they had 3 large luggage gloves, but because of a technical phone issue I could not call them prior to my trip down to the store. Where I then arrived to be told that their system could not accept my receipt and I must purchase it and go back to where I had bought the one I was looking to exchange. What is the purpose of having an exchange system if I can't go to any branch and exchange an item I gave no problems when purchasing, now that I want to exchange it for a bigger size then there must be problems. Really makes shopping an head striking inconvenience.