We have a live-in doctor if there's a problem I can't handle.
假如我遇到不能解决的问题 ,我们还有位驻家医生。
A word spoken is past recalling.
一言既出,驷马难追。
and there is a very firm rule that the bank has no right or authority to pay out a customer's money on a cheque on which its customer's signature has been forged.