Merging Scenarios and Current Schedule Issues

In OPC, I've been trying to merge an older version of the schedule that a trade partner gave us with additions to the schedule, with my current version of the schedule. They included their changes in a new, separate WBS section under the WBS of where they go. But each time I've tried to merge the two, all of their activities will not merge, and I get the reasoning as "Cannot merge an activity with a WBS that has the same WBS Code and WBS Name as a sibling WBS". Since I can't find a way to change the WBS