HLR requests are not suitable for checking the availability of subscribers in real time.
Information obtained from such requests is cached by the operators and may give irrelevant information for a day or more. To check the availability of subscriber numbers in real time, you can use PINGSMS.
This service is more intended to check that the subscriber is not blocked and has recently been online. This is useful for cleaning the subscriber database to remove those that no longer exist from the mailing list.