Issue with Employee ChangeEmployeeID Action

I’m struggling getting the Employee ChangeEmployeeID Action to work.  In Postman I’ve setup the following:

Verb: PUT

URL: <host>/entity/Default/20.200.001/employee/ChangeEmployeeID

BODY:

{

"entity": {"EmployeeID": {"value": "{OldEmployeeID}"}},

"parameters": {"EmployeeID": {"value": "{NewEmployeeID}"}}

}

I’m receiving the following error: 

"Specified argument was out of the range of valid values. Parameter name: Invalid uri structure"

Does anyone have a working payload for this action?

Thanks in advance