HLR is an excellent tool for checking the recipients' database from incorrect or inactive phone numbers. Periodically, your telephone numbers database needs to be cleaned, because your customers can give you incorrect phone numbers when filling out the questionnaires or provide you with incorrect information for registration. This carries additional costs for you, because when you send SMS campaigns to "bad numbers", you also pay money for these SMS. You can save your money and spend it more profitably by checking the numbers using the HLR service.
HLR (Home Location Register) — is a a set of information about subscribers of mobile operators from around the world, which indicates the current status of telephone numbers in the network of certain operators at a given time. This database of numbers is updated regularly.
Ping-SMS — is a special message that is sent to the subscriber's phone in hidden mode and is not displayed on the screen. You can find out if the subscriber is available at this time, whereas the HLR request allows you to find out information about the telephone number only at the time when the common database of numbers was updated.