I visited Jogja last weekend and had dropped by at the Tourist Office at 56, Jl Malioboro. The lady at the office was most helpful and recommended a few places to visit. I signed up for a Ramayana Ballet at Prambanan for Saturday 6th Oct after providing my hotel details and made the necessary payments.
On 6th evening, I waited for more than an hour in my hotel lobby but nobody came to pick me up. I also checked with my hotel desk and nobody had called for me.
I tried calling the Tourism Authority office, but it closes at 6 PM. The transport operator must have made a mistake but this resulted in a very frustrating experience for me. Just wanted to advise others to make sure they get the transport operators contact details to avoid getting into such a situation.