My complaint:
We have waited for hours in order to be able to buy tickets to Coldplay but the queue was so long and when our turn finally came, most of the categories were already sold out. We can now find a lot of overpriced tickets on viagogo (exactly for the categories that should have been sold out). It is not okay to not be able to buy tickets because other people buy plenty just to re sell them.
Suggested solution:
Cancell all the coldplay tickets from that website or shut down the website since it is illegal to re sell tickets.
