Your contract clearly states that freighter flying is voluntary. So unless you write to the company and state that you will fly the freighter, they should roster you in accordance with your contract, not the other way around.
This is again a clear violation to your contract and this is how the company interprets your contract. There is no reason what so ever to have a letter on file that allows you not to fly the freighter, quite the contrary.
If the AOA would grow some balls, ask a lawyer and have a letter sent to the company stating so, maybe the PW will stop doing the !!!!e that he is doing.
IMHO, if you are rostered to fly the freighter, just call in sick, unless you don’t mind having your contract violated.
But I doubt many will do that.
