Are you charged to forward calls from one three mobile number to a different three mobile number.
Welcome to the 3Community @Brita_82084. Yes if you forward a call from your number to another this call will come out of your available allowance, if you don't have any minutes available you'll be charged at the standard call rate.
If you'd like to have a look at call rates click here
Is it possible to forward calls to an international number?
Hi @Add_11923, I honestly didn't know this myself, but I've just confirmed that it's not possible to forward calls to an international number.