In this case I am right though
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Opening a line of communication to a suspended client's VPS before invoicing would be the best thing to do instead of just throwing them an invoice and 'hoping they submit a ticket'. I have a feeling I know you know this but just don't want to say it because it saves you time with dealing with suspended clients. And I am telling you, if you were to do it my way you would retain a larger customer pool. But wait, the customers are always wrong right?
Unless, ofcourse, their suspension was due to a massive DDoS and then in that case, yea, you have the right to terminate them. But by that point, an invoice wouldn't of been sent.