Lawyer to legally represent us against a merchant

General information for the business: We sell furniture
Description of legal work: An online daily deals website has send us an unexpected bill of 7300 pounds claiming that their customer returned the goods to us last year.

It seems there was an error on their processing system and they were refunding the customers AFTER we had delivered the goods. It got spotted on their half year internal review. So the customers have the goods and also the money.

Instead of accepting the loss, they are pursuing us for this sum claiming we gve auhtorisation for a refund and that their customers returned the goods to us. Both of these are not true and they have failed to provide any evidence to support their claim.

Despite this they continue to puruse us for this sum.

We need some one to represent us legally to exchange correspondence and if needed, to represent us in the claims court.
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