Going by the price paid (did you only pay the $1.80?) you have now sent the item as a large letter. Additionally, it also appears that you have sent the item without tracking information, so you may have a few anxious days instore for you wondering if your item was delivered. If it isn't, and the buyer opens up a INR case in PayPal, then you will be required to provide a tracking number and proof of lodgement, or PayPal will likely find in the buyer's favour and issue them a refund.

Well, you do have to pay for C&S online via PayPal or credit card, but the system won't allow you to print the label before you pay.

If you had previously paid online, contact C&S and request a refund as you have not used that service. An email is fine, just include the AP Article ID and a short line - please issue refund as I will not be using this.