Mistake - Credit increase

On the 25th Nov 2015 i received a statement from Foshini stating they have given me a credit increase, I purchased something on the very same day an the credit increase reflected on my slip.<br> On Saturday the 05 Dec 2015 i again purchased something at Foshini only to find out that i dont have enough credit to purchase the item as the credit increase was not given to me, i then had pay cash for the item.I went to Fashion Express to check if Foshini did not make a mistake with my account as i could not understand why i had no credit.The Girl behind the counter checked and confirmed i had no credit i explained my story to her she called the accounts department an they responded with \ It was a mistake i should have never gotten the credit increase". What dont understand is why there was no correspondence from the accounts department stating they had made a mistake with my account instead they left me standing a the counter on Sat thinkn i have credit"