let me explain you what happens if you wanna transfer some $ in CC.
you (cust_ID x) wanna send 1 euro to cust_ID y , cc send to

a message with this request ->

check this request on ivan server -> if it's ok the money will be transfered, if not you will receive an error messange (ERR Not Enough money).
i can put in my CC, how many euros i want; but unfortunately it's only visible ;p