OSD locked in viewsonic n3000w

How do I unlocked OSD locked in viewsonic LCD TV n300w?
There is no up or down arrow in remote control or on the LCD TV.
Do I keep the TV on when I press the combination of the buttons that you suggested?
The manual of n3000w suggests that push power button and up button at the same time but it doesn't work for me. Is this up button referring to channel up or voice up? there is no specific up button on the LCD TV or remote control.
I called the customer service of viewsonic and he told me several combinations of pressing the buttons but still didn't work. Then he said that he can't help me.??