I just went to book two tickets on KLM and tried to use the vouchers which were issued to me when they cancelled my flight in 2020, due to covid. The vouchers were originally valid until 31/12/2021, but have been extended for 6 months.

The website wouldn't allow me to enter a voucher at all. I rang their call centre, and they said I can only use 2 vouchers per passenger. When they cancelled the flight, they issued 9 vouchers for 2 passengers. That was KLM's decision, not mine. Is there any way around this problem? I want to be forearmed when I call back. I asked to speak with a supervisor and she said that there wasn't one.