How to add or change the dialing prefix on the DM300C, DM400C and more

Learn how to add or change the dialing prefix on the DM300C, DM400C, and DM475.
Products affected: DM300C™, DM400C™, and DM475™
Use the following steps to add a prefix number before dialing an outside line:
  1. Press Menu
  2. Press Page Down
  3. Select Data Center Options
  4. Select Phone Settings
  5. Select Dialing Prefix
  6. Enter the prefix number wanted (such as a "9") and select Accept.  The Phone Settings menu returns.
  7. Press the Home key to exit the menu

UPDATED: 14 August 2021

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