Mytrip.com complaint: Repeatedly asking for more money but no flights booked

I booked flights to New Zealand for September 2020 however this was cancelled due to the pandemic. The tickets were transferred to a Flexi ticket. I phone their customer service team on 24.05.2021 to rebook flights. There was a difference in price which I was sent a link via email to pay. This was paid. During the same night , I received another email saying there was an extra £4 to pay, the link didn’t work at first but I was able to solve it the following day and pay for flights. I then received my travel documents and it was the flights I booked last year, it even stated 2020. I phone the customer service team back and explained, the guy on the phone told me he would sort this out and I would receive the correct travel document in the next few hours. I did not recieve the correct travel document. I then today recieved another email asking for further payment. I have called the customer service team, I was hung up on when he put me on hold to find out what was going on. The service I have recieved is appauling and I am worried this is a scam. During this time, I have been hung up 3 times by the customer service team.