Getting a Premium ID for a LINE Business Account allows you to change the random string to your business name, if available. This is especially useful if you have an unverified account, which is only searchable via ID.

LINE charges USD 12 per year for a Premium ID and you can upgrade at any time. You can upgrade to a Premium ID in the LINE Official Accounts platform. But note that Premium IDs are not available in the USA, Singapore, and EU.
You can access this option by logging in to the Line official account manager console and navigating to Navigate to Settings > Activity and Billing > Premium ID as shown below: