I purchased a new camera from an online retailer which is suspicious as the serial number on the camera doesn't match the serial number in the menu, there was no production sticker on the box and the manufacturer's security tape was missing. Irrespective of the reason, I have decided to use the 14 day money back guarantee which the online retailer gives:

“We offer a 14 day money back guarantee on all of our products so if for any reason you are unhappy then simply get in touch with us and we will authorise a return and full refund. We offer a 14 day money back guarantee. Simply email us to obtain authorisation for your return within 14 days of receipt.”

But when I send emails to them there they don't reply so I want to claim under Chargeback but I cannot see my case fitting within any of the reasons on the Tesco Chargeback. Which section should I use?

Many thanks for your help.