Not happy with Builders Warehouse

I am not happy with Builders Warehouse. I have a credit card with them, but whenever I go to buy some material, my card doesnt seem to work. Yet my monthly repayment is always paid up on time and up to date. I called their call centre to report the problem and they told me the card is old I need to get a new card. I went to their store at Umhlanga KZN and the lady there advised me that the person who issues cards has left for the day and she left with the keys. I thought that was poor service, if one person is gone that doesn't mean that the business cannot proceed. I need help with Builders to fix my card so I can be able to do shopping. Thanks.