I had real problems with Viator. I was given a contact number for the local operators of the tour and told that I must confirm the trip the day before travel. I spent over an hour and half trying to get through on the telephone on the number given - this cost my daughter over 50 Australian dollars as I was using her mobile phone. We contacted Viator on their website - where they promise a 36 hour reply. We explained that we did not know where to meet the tour bus and that this was really urgent. They did not reply - at all! We managed to find the tour bus, and the local operator explained that the number we had been given was for travel agents and is rarely answered! The tour itself was very good - but Viator's customer service was very poor and, in total, cost me more than 100 Australian dollars on phone calls and taxis trying to find the tour bus!