Air Transat complaint: awful service and took my money

We have booked flight tickets to Canada from UK in 2020. Due to covid outspread we couldn’t go and after speaking to airtransat on numerous occasions and they have offered a travel voucher. However, it wasn’t 100% of our costs. they offer was worth £1926,48 (around 8090%).
After 2 years we have finally decided that it safe to go to Canada and contacted the office 2 weeks ago to book new tickets as per the instructions on the original email. I have been on the line for 30 mins, and I was cut off, then I was on the line for 1hour and 30mins. In the meantime, gentleman answered and said he needs to transfer me to the different department. After that woman answered and she was arguing with me that I’m not in the right place and suddenly she cut me off. After a little while we tried to call again and we were on the phone all together 2 hrs. The lady was nice, and she said she can see our vouchers and she was able to book new tickets for us. The lady took my credit card details and finalised transaction. New tickets costed £2334.61, and our vouchers were £1926.48 so my card should be charged £408.13. Unfortunately, the lady forgot to use the voucher and charged my card whole price of £2334.61. She did apologise and said I will receive a refund however, so far, I haven’t got it.
Overall, I’m disgusted with the service we received, and I would never recommend the company to anyone to deal with. Half of your staff are not informative and don’t know what they are doing.
We have spent 4 hours on the phone to you all together, I have been charged £68.25 from my phone network and on the top of that you took so much of out money! My credit card will probably charge me some interest fees too. In general we have lost so much money already!