How is the register HLR?
HLR register contains information about all GSM networks subscribers. It’s automatically updated every time the mobile operator activate new numbers. These numbers are stored in the database until they no longer used. When the system recognizes that phone numbers are no longer available, it removes them from the database.
Checking the phone number with HLR request is absolutely anonymously. The subscribers, which numbers are checked by HLR Lookup won’t know about it.