To contact the fiverr’s manager, what shall I do?
Did you communicate with your seller and did you tell him/her you would like a refund? Communication goes a long way. You can open the order and click on “Resolution Center” there you can request a refund if the order has not been closed yet. You can also contact customer support for assistance.
The answer you have been given is the best one. If you contact CS without talking with the seller, they may encourage you to talk with the seller first. If you have a legitimate cause to get assistance, though, Customer Support will help.