Rail union RMT has rescheduled a strike calling off a three-day walkout from December 22 to replace it with a 48-hour stoppage from December 19.
The strike, surrounding a bitter dispute over changes to the role of guards, changed the date of the walkout following consultation with passengers and members.
RMT general secretary Mick Cash said: "It is from that daily feedback from passengers that the union has taken the decision to alter the dates for action over Christmas. That's the difference between us and Southern. We listen, they don't."
Strikes scheduled for December 6 to 8 and from New Year's Eve to January 2 remain in place.