Transportaion module - Set up flat rate


i am trying to setup a flat rate from different cities to different cites.

what is the best way to handle it?

As it is a flat rate , i dont want to use "breack unit" field on the Rate vase screen but it doesnt work . i have this message: Unexpected error occurred when processing request. Please verify server event log or contact administrator.

Any help on how to do the correct setup will be appreciated