M5350 
3G Mobile 
4.3.5 SMS Settings
On this page, you can do the following settings:
Figure
Message Center: Disabled by default. It's recommended to keep the default setting. If you want to manually set the Message Center Number, please select Enable.
Message Center Number: When the Message Center is enabled, you can enter the Message Center Number of the local ISP. If you enter a wrong number, the SMS would be affected and not properly used.
Save the Delivered Messages: Enable it to automatically save the delivered messages in the Outbox.
Auto Replace Old Messages: If enabled, it will automatically delete the oldest message and save the new one when the Outbox or Drafts box is full. If disabled, you need to manually delete the old messages to save the new ones when the Outbox or Drafts box is full.
Click Save to make your settings take effect.