The call handling limit of the Free Edition means that exceeding 3 simultaneous calls will shut down HAAst (and implicitly Asterisk with it).
The Free Edition allows you to test compatibility, features, usability, etc. which is usually sufficient for a trial, or even for a small office wishing to create a cluster. The Free Edition is not designed to handle the full call load of a mid to large size business, nor offer all features (of the Commercial Unlimited Edition).
If you wish to conduct a pilot with all features enabled and capacity limits removed we would be happy to work with you on the pilot (see https://telium.io/faq1002) and provide a temporary Commercial Unlimited Edition license.