As it says on the festival website

HOAX WARNING – several scammers are at work, cutting and pasting sections of copy relating to the Jazz Festival and spamming databases, pretending to make an offer for bands to take part in the Festival, conditional on them paying some items like visa costs or a travel contribution. They are operating under several names, but they are nothing to do with the Festival.   We never ask for payments to take part in the Festival, and we are looking at legal options to end this abuse.   If you know anyone who has been approached in this way, please tell them not to be fooled. We are very sorry about the disappointment and confusion this has caused.