This article is meant to navigate you through Viberer pricing.
Oapps for Viber costs $7.99 per Zendesk subdomain per month. You can add up to 4 Viber channels to one Zendesk installation without any additional fees.
The 14th-days free trial will help you investigate all the advantages of the app from inside. To use a free trial you should install Oapps for Viber from the Marketplace. When you install the application, you will still be asked to enter your card details - this is a Marketplace requirement, but no charges occur until the 14-days trial period ends.