Park Plaza Westminster Bridge London Reviews

I stayed at the Park Plaza Westminster Bridge for 2 nights. I booked and pre-paid for everything on Trip.com. At check-in, I was told the upgrade to a Studio would cost £50/night, hence, £100 for the two nights. I agreed to the upgrade and paid for the £100 at check-in. At check-out, my card was charged an additional £100. The staff told me the upgrade was £100/night, £200 for two nights. He gave me an invoice. I immediately disputed the extra £100 charge, as that wasn't what I was told and agreed to at check-in. He got another colleague to look at the system, and she confirmed I should not have been charged the extra £100. (The price difference between the room type I booked and the upgrade on the dates of my stay was only £43/night), so charging £50/night for the upgrade makes total sense.) The front desk staff told me I would be refunded the £100 immediately and they will email me a new invoice with the correct prices. Over 2 weeks have passed, I have not seen a reversal or a refund to my card, and I have not been sent a new invoice. Worst of all, I kept calling up the hotel and they said there's nothing they can do and told me to email the Admin team. I emailed the admin team a number of times and had no response, not even an automated email receipt. This is simply appalling.