[BUG] Billing and Transfer Money to another account.

Hi, in Astpp its very big bug in billing system. i think ver.3 have same bug.
1) create two account, for example user1 and user2
2) recharge user1 with 5usd.
3) make calling with user1 to destination 1 (client in another site answer and talking)
4) in this moment user1 transfer all money 5usd to account user2, in this moment user1 have 0 in account and user2 have 5usd. user1 talking about 24minuts free.

can you make change in billing system? if user1 calling, or start calling, in moment transfer money to another account, check if, client have active process and reject transfer money.

sory for my english.

thx. Alex.