Yes. The ticket amount can be changed before the client pre-pays (and settles the contract).
No, you can publish as many tickets as you want for free.
No. Cancellation is possible before you complete payment (settling the contract).
Please complete the payment by using your registered credit card. If you don't have a credit card, please follow the instructions on the payment page and create a bank transfer, and then contact ANYTIMES support once you have made the transfer.