When trying to change the call type for a call within Customer Care if the following error message is received:
"Invalid characters in datetime/datetime-tz value (11841)"
The reason for the error is that one or more of the issues that are linked to the call are missing a time. In this instance the call type is may originally have been an SLA call type therefore a time must be entered on the issue/s. Once you add a time to the issue/s then the Call Type can be changed successfully.