Just so I get this right, your client lets her account go negative, and then writes herself a check that is drawn on another bank, correct? This what lots of people try to do to cover their accounts until they have real money. Don't blame the Bank, blame your client for not staying on top of her finances. And if she goes negative again, writing herself a check drawn from a different Bank will cause the same type of holds for all Banks, not just Zions.