When 00 is typed, a complete number appears in the window of the phone. When the call is answered, one zero disappears, and the window of the phone displays just 0.
There are two options:
In the private branch exchange (PBX) configuration, disable the sending of the connected number information element in the connect message.
In Cisco CallManager 4.2(3) or later, the parameter can be found under Service Parameters > CallManager > Device > General > Always Display Original Dialed Number.
This parameter determines whether phones always display the number that the caller originally dialed, which does not always match the final connected number. If Cisco CallManager routes the call from the originally dialed number to the connected number with a call forwarding directive, a translation pattern, route pattern, a redirection by a CTI application, or other means, this parameter determines whether the connected number or the originally dialed number is exposed. These are the valid values:
True display the originally dialed number
False display the connected number
Note: This is a required field, and the default is false.
Refer to Cisco Bug ID CSCsd04254 for more information.