Lastminute complaint: Voucher refund scam

I am writing with regards to my unpleasant and poor experience with LastMinute. For some background, I made a flight booking with LastMinute.com travelling from London to Miami. Closer to the travel date, I was informed of flight changes with alternative flight options on a different day which was not ideal for me. I therefore requested a full refund and was offered a voucher for the same monetary value.

While carefully enquired and was given the assurance that the voucher could be used multiple times until the balance is fully utilised, and for argument sake let us assume the balance was £1000.
Recently I used the voucher to make a hotel booking worth £500 which was fully refundable without any cancellation fees. Given that we would have been renting a car, I contacted the hotel to arrange for a parking (which was mentioned on the website before booking) but to my surprise, the hotel was charging what I considered unreasonable for overnight parking.

I therefore decided to cancel the hotel booking, and was issued a full refund but by means of a second voucher of £500. Now I have two vouchers worth of £500 compared to an initial voucher of £1000 and that is mainly because LastMinute decided to refund with another voucher rather than crediting the amount back to the original voucher.

I go ahead and make a hotel booking for £750 and was trying to use my vouchers and realised that you can only use one voucher per booking. I immediately contacted LastMinute for clarification as they refunded with another voucher and their response was that I’ll have to use one voucher and pay for the extra £250 and then use the second voucher for another booking. This is completely unacceptable as first I was not informed about this prior to being refunded and second it is completely unfair as it is a problem which sources from the fact that Lastminute decided to refund with a new voucher rather than just crediting the original one. Hence I believe it is pure dishonesty and would even call it a scam where consumers are being purposefully deceived and robbed.

What is more shocking is the customer team did acknowledge that it is not sensible what happened but at the same time nothing.