Refusal to honour guarantee

In March we purchased an electric blanket from Yuppiechef Westlake. As they are near us we did not use their delivery system but bought it over the counter. This was at 16Mar 11:23 using a Visa card. Unfortunately we only have credit card proof of this purchase and it appears that Yuppiechef never entered the sale into my 'account' so there is no purchase reference in their system. This makes it impossible to enter a return claim via my account and the requests for them to honour the guarantee merely result in a 'use the claim system' email which is impossible. A promise for a return phone call was not fulfilled.