These are the hotline numbers. Calling these numbers is free for your customers. It can be useful for customer support, online store or a large trading network, if your business is focused on a particular market.
The owner will be charged for incoming calls to such numbers. There is up to 30 channels available on one number (you can receive 30 calls at once). Usually customers can call these numbers only within a particular country. It is worth mentioning that outgoing Caller ID calls are not compatible with this kind of number. It only receives incoming calls.