Originally Posted by
WaldronS
....
When they call me back, can they insist I have to cancel/rebook just because they can't figure out the price?
No, No and No.
Voluntary cancellation/changes by a passenger are not the same involuntary changes by the airline. Refer to EC261/2004 comment above.
With the "
only the outbound flight that has increased so much " --> Not your problem as, you have not changed the outbound date. You should not be charged extra for something you have not done.