I sent 2 e-mails 3 days apart on the cancellation. This could not be done by "Manage my bookings" bcoz it said that my reservation could not be found, in spite of the fact that I have a #BR- number booking reference.
It has been quite frustrating trying to get Viator on the line to talk to a real person as none of the FAQs help. Found this "pissedconsumer" link to a phone call. Talked to a very nice lady named Jane and she helped to cancel and send the e-mail confirmation all within 5 minutes. Fantastic.
I suggest that you have a "Contact Us" in the Viator website to this service. I'm very sure your approval ratings will go up significantly.
My cancellation is done bcoz of change in travel destination. I intend to book some other tours with Viator right after this.
Reason of review: Good customer service.