During development, it's best to have a developer channel to test rather than using the LINE Official Account in production.
Creating a LINE Official account is free. To create a free account, go to: LINE for Business and complete the steps described. There are three different subscription plans including a Free plan that provides free messages a month. The number of free messages will depend on your location.
The Sinch Developer Documentation site contains comprehensive documentation and tutorials, which show you how we support LINE through the Sinch Conversation API.