nicocicconep, I don`t know how to support better than
Fernanda Alves already did, because direct contact with promoters is really best way in this situatuon, but I`d like to cheer you up with own little example: last year my two friends visited two different events organized by same promoter and had same problem (Russian post works not so fast also

().
So they wrote to promoter and asked if they can pay for the ticket online but take it in the office on the day of the show. Both times it worked! I`m not sure if it is common practice, but still you may ask about this variant too.
And also you may try to write to promoter not only on e-mail, but also (if this concert has page in Facebook) in social net. Sometimes it is even faster... GOOD LUCK!!!