I am not resonsible for Superbalist sytem glitches

Ordered, paid for and received confirmation for a watch at Black Friday 60% discount. Next day Superbalist cancelled the order, refunded and offered a 10% discount voucher as apology for a glitch in their system. This is unacceptable and *******. We have entered into a legal contract of offer and acceptance and Superbalist must fulfill the order. My correspondence is responded to with inappropriate form-letter emails that do not address the issue. .