Zte MF275R User Manual page 26

Note:
[DelaySec] represents the duration in seconds before
the call will forward.
(Example: *61*1234567890**10# forwards your calls to
the phone number 123-456-7890, if you don't answer
the calls for 10 seconds.)
4. Wait for 3 seconds and until you hear a confirmation
tone for the forwarding to complete before hanging up.
Note:
Press #61# to un-forward calls.
Forward when unreachable
1. Press *62* on your connected phone.
2. Dial the 10-digit number to which you wish to forward
your calls.
3. Press "#" key.
4. Wait for 3 seconds and until you hear a confirmation
tone for the forwarding to complete before hanging up.
Note:
Press #62# to un-forward calls.
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