What happens to all the SMS messages that don get delivered?
When you send an SMS, the “message sent” acknowledgement is confirmation that the network has accepted the message. If it can’t be delivered it is stored on the SMSC (Short Message Service Centre) and a message waiting flag is set on the HLR (Home Location Register). When the subscriber registers with the network again the HLR sees the flag is set and sends a command to get the message delivered. If for any reason the message expires before it can be delivered the SMSC will cancel the message waiting flag, cancel the billing request and delete the message. If you are on pre pay then a credit will be made back to your account for the price of the SMS as you actually pay for a message to be delivered, not to send it. However as pre pay subscribers work on a credit basis the cost is debited immediately and credited back if necessary. If you have any questions don’t hesitate to give me a shout.
