Superbalist stole from me and refuse to give back my money

I shopped on Superbalist on Black Friday/27 November 2020. I notices upon completing my order i was charged the full price on an item instead of the Black Friday price. I immediately called the call centre and logged the issue. I was clear in my responses that i DO NOT WANT CREDIT, i want the money sent back to my card used for purchase. On 2 December they tell me sorry, here is a voucher for the overcharge amount, no surprise the voucher also came with a bunch of conditions: 'The promotion applies to all products. The promotion excludes products which aren't shippable. The promotion excludes products on sale. This promotion isn't available at the moment. The promotion is valid after 27/11/2020 00:00:01. The promotion is valid before 31/12/2020 23:59:59. ' To which i rep**** i do not their credit, i want the money back in my card. on 2/3 december they then respond saying they cant do anything, even though this was their error, and here is the voucher, again with all kinds of conditions, forcing me to either lose the money , THAT THEY STOLE FROM ME TO BEGIN WITH, or shop on the same website that stole from me in the first place. On 3 December I have since responded that i do not accept this and i do not for one minute believe this is all they can do. on 3 December i also tried logging a return , surprise surprise, the app says "an error has occurred" so i am unable to log the return.