Focus on the Briefcase: The briefcase in the mission contains a tracking device you need to plant on informant Franz Kraus. It's not a phone or communication device.
No Phone Calls in the Briefcase: The briefcase doesn't have any connection to phone calls or transferring calls.
Mission Objectives:
The mission revolves around locating Kraus and the briefcase, not phone calls. Your main goals are:
Infiltrate East Berlin: You need to navigate the city undetected.
Find Kraus' Apartment: Afghanistan Phone Number List Locate the informant's residence.
Plant the Tracker: Place the tracking device from the briefcase on Kraus.
Decide Kraus's Fate (Optional Player Choice): Depending on Adler's instructions (and potentially your choice), you can either capture or eliminate Kraus.
Possible Misunderstanding:
There might be confusion because the mission involves locating a briefcase containing a tracking device. However, this device tracks people, not phone calls.
Overall:
"Cold transferring a call" is a real-world phone communication concept entirely separate from the gameplay mechanics and story of "Brick in the Wall" in Black Ops Cold War, even when considering the briefcase objective.