Archived:SetCallForwardingStatus returns -6 in S60 2nd Edition (Known Issue)
SetCallForwardingStatus() can be used to divert voice calls to another mobile. However, when this is used on S60 2nd Edition devices, it returns the status KErrArgument (-6).
SetCallForwardingStatus() is the RMobilePhone API used to divert voice calls. The API RMobilePhone::SetCallForwardingStatus() returns KErrArgument (-6) when Registration, Activation, and Deactivation of the number that is to be set for divert is done. However, the call divert goes through.
No solution currently exists. This issue is not expected to be fixed in future releases.