4524is a SMS 365, enterprise service status code, which indicates that the MSISDN has been blacklisted.
Reason for a 4524 response
The reasons why the 4524 status code is returned, and the actions which should be taken, are described below:
The end user’s MSISDN is not reachable due to a blacklist process.
The end user should be informed that their MSISDN has been added to a blacklist.
A request to blacklist can be due to a single, problem service number sending unsolicited SMS MT messages to the end user.
If they wish to remove this blacklist, they should contact their network operator, providing the service number from which they wish to receive SMS MT messages, so that the network operator can request a whitelist.
Note: The whitelisting of any MSISDN must originate from the network operator to which the MSISDN belongs.
The network operator owns the relationship with their end user, and can advise them accordingly on any additional outcome of whitelisting the MSISDN.
Many MSISDN for a single destination operator are blacklisted.
Raise a ticket to the Digital Interconnect Service Desk (SD), detailing the OrderID, MSISDN, operator and date/time the MT messages were sent, so that the SD team can investigate.