So, today a tug of war was played with the slave caller mechanic trying to free / keep a slave.
The following was observed:
+ There is no counter / way to stop / way to interrupt a slave caller at all (unlike yoink or lenses which can all be interrupted). Even casting ward teleport the moment the collar starts burning does nothing to prevent a slave being called.
+ There is no limit to how many times and how quickly a slave caller can be used (this slave was constantly called back immediately at every escape attempt)
+ A slave can now be called even when they are entirely disguised (a yoinker can't even do this if they don't know the disguise name)
With the above I think there should be a way to interrupt / block / stop a slave caller's call. I also believe that if it should be decided that somehow the caller can find someone by their true name, perhaps a roll should be made against someone's bluff, perform or Hide/MS skill when they're disguised (which could open up more escape RP by kitting people with disguise gear etc.) or hidden.