Can you unregister from a WSOP event after preregistering?

[MLSchaff]

What if you are still in an event at another casino and can prove it - like making it to day 2 of a Bellagio Cup or Venetian Deepstack event that conflicts with a WSOP event you have already paid for?

Any chance they would let you either unregister or change your registration to a later WSOP event?