Samsung SCH-8500 - Manual (Page 97)

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Your Sprint PCS Phone can store up to 100 messages,
depending on the length of the messages. When message
memory reaches 75% capacity, the screen displays “Memory
is 75% full. Erase old messages.” At 100% capacity, the screen
displays a text notification and rejects additional incoming
messages until you erase the stored messages.
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Incoming messages are received even when your phone is in
Lock mode. However, the screen will display the time and
date of the message but you cannot access the message. To
access the message, unlock the phone to proceed.