Thanks to everyone for the answers.
Another question is regarding gift certificates.
I noticed that when a customer creates and pays for a gift certificate, it stays permanently in the cart. Deleting or removing it from cart is not possible. The problem with this is when that customer adds another product to cart and tries to pay for that new product only, the order adds the certificate as well. There is no way to pay for only the new product.
I as far as I remember, this bug will be fixed in the next version. You can contact support team for the fix