The change shakes up PR reporting lines, with responsibility for internal comms set to be handed over to HR director Daniel Cloke, in line with wider global practice at the mobile phone company.
Meanwhile the external comms, reputation and responsibility and social media teams are now set to report to corporate and external affairs director Helen Lamprell.
Cull is still playing a role in the process of replacing outgoing director of external relations Richard Wray, according to a spokesman for Vodafone UK.
Explaining the changes, he said PR "will be working more closely with key colleagues in other departments".
The moves are understood to be part of a tightening of the top team advising Hoencamp, who replaced Guy Lawrence last month.
Cull, formerly head of comms at holiday company TUI UK, joined Vodafone last summer.
Since then, he has worked on the launch of 4G and the integration of the former Cable & Wireless with Vodafone, and has reported directly to the CEO.
Cull said the departure was "very amicable", adding: "it’s business as usual for now, we’ll start afresh in the New Year."
Hoencamp, a former marketer, has worked at Vodafone since 1998.