Sometimes you may need to change the owner (merchant) of a campaign. Here is the way how to do that:
In the network owner (admin) panel navigate to Start -> Campaigns -> Campaign manager. Click edit (pencil icon on the right) on the desired campaign so the 'Edit campaign' window shows up. Select the 'Edit details' tab and scroll down to the 'Campaign account' section. Now click the drop-down button next to the 'account' label to select the desired owner.
After this action scroll down to the bottom of the page and click SAVE.