Couldn't make any calls (by 2 users)

Hi,

All the lights in the device were "on" and couldn't make any calls throught the device.
When tried " No link to the Base Phone, move near the base phone and try again" is the error message displayed in the handset.
A small kid pressed some button and since then the problem raised.
we Don't know what he pressed.

Detatched all the plug-ins and attached once again.
Tried pressing all the buttons
Checked the adapter too but of no use.

Can you please let me know what can be done in this case.

Thanks & Regards
Udaya