Wowcher complaint: Withholding refundcredit money

Wowcher will not credit me back the £109.99 that is mine to spend as the date expired by one day. I was away finally visiting my parents for the first time since February 2020 and we were delayed leaving for the holiday as my eldest son had a positive test for Covid a few weeks ago and we all had to isolate and delay our visit. Luckily he wasn’t too unwell but the last thing on my mind whilst seeing my parents was spending the money on things we didn’t need as there was nothing available when I last looked that I wanted to buy. I even looked for a one-night hotel break but no convenient dates were available. The money was spent originally on a mattress for my younger teenage son, he was excited to be allowed a double bed, but the mattress was the worst quality I’ve ever experienced, as if the spings were going to pop out, it was terribly uncomfortable and it wobbled! We went through the slow process of returning it only to find that I couldn’t have a refund, only a credit. There were no suitable mattresses that I could afford and I ended up buying a good one from Amazon. I didn’t want to spend the credit frivolously as I can’t afford to do that and was waiting for an appropriate offer for a night away with my sons or a birthday present gift. When you return a terrible quality item that is not fit for the purpose you don’t expect to have your money taken from you, times are hard and £109.99 is a lot of money. I have had 3 attempts at conversations with Wowcher through WhatsApp, all very time consuming, the outcome being an abrupt no, then cut off. I had also asked for a phone number for a manager or for one to call me but that was ignored at least twice and no one called. Their customer service is terrible, hard to get hold of and then when they don’t like it they just cut you off knowing it will take you many messages with a bot before a wait of up to 15 hours before a human contacts you just to say no, sorry and goodbye!