Demanding double payment

I ordered a jewellery box at Home choice and paid cash for it. On the day i paid for it i paid my account as well, they phoned me and told me that i haven'd paid my account, i told them i did and gave them the reference number on the receipt and said they are going to trace the payment., few days later they told me i had to pay again because the can't trace the payment, but it was strange because i used the say reference number for both payments of the account and the jewellery box, but they can only see the payment of the jewellery box, how possible is that, i still got my receipt and i won't make the second payment because i can see they are trying to **** me.