[Lemur]

Usually I only contact zavvi after 30 days through their website. Login to your account and under the order there is a query button. They take 1 -2 days to reply. If after 2 days no reply spam more.

They will send you a declaration form either by mail (this takes around 1 week to reach) or by email. You can select store credit, replacement or refund on the form. Then sign and email to them.

If at any stage they screw up, spam them more until they get it right.

Some examples of screw up from them:
Customer service said form will be emailed and no email received
Email received but no form attachment
Email signed form to them and no response (they said they didn't receive and will send a new form)
Claimed that refund processed but I didn't receive refund
Confirmed again that refund is given but I didn't receive

For all the above, just keep spamming them until they get it right