You can check phone numbers for availability by sending a special HLR request. As a result of executing the request, data will be received about the subscriber's country and operator, about the roaming operator when the subscriber is on someone else's network, as well as about the subscriber's status (available or not). Subscribers, owners of the numbers being checked, will not receive any notifications about the checks performed on their number.
Execution of an HLR request over the HTTP protocol is performed in the same way as sending an SMS message,
and the request must pass an additional parameter hlr=1.
To send an HLR request, use the GET or POST method to call the address:
https://smscentre.com/sys/send.php?login=<login>&psw=<password>&phones=<phones>&hlr=1
Other parameters that are used for sending regular SMS messages and described on this page are also available.
The result of the HLR request can be sent to the URL for receiving incoming messages and statuses
specified in the settings in your personal account, or it can be read by requesting the status of the sent SMS message.
Sending an HLR request