Just an update: I sent a bank statement yesterday morning and 24 hours later they haven't replied at all. Called the hotline and asked what's up. The agent told me that they received the additional documentation and will decide with 24 hours whether they reactivate my credit card. I asked whether the agent could just cancel the booking and the agent casually told me that it is cancelled already and if my card is marked as valid again in the system I could book again and they would respect the prices I got at the time of booking. I asked him whether I could have in writing via email that the flight is cancelled and I would have to actively rebook it, but the agent refused to send an email. Since I am at a point where I cannot just believe the information that I am getting, I have to wait more.

So, flights are cancelled and nobody told me that. Phone agents cannot do anything. No reaction to my email for two days is ok for them. No reliable information can be documented via email.

I hope I am getting out of this mess soon. At this point I am looking forward to be able to book the flights with Avianca instead, and that's saying something.