Canceled AT&T wireless order

I placed a order for an iPhone 7plus I paid 260 down then I got an email 4 days later saying I would need to make another deposit so I canceled the order. I contacted AT&T they told me it would take 3-5 days to get my money back here it is 7 days and still no money. I don’t understand how they can take your money so fast but can’t refund it back quick!