This is all about the communication; keep your client informed, make sure that all they need to know is on this page (at any time), and they won't need to phone you. I've drafted a rewrite of the text, giving more emphasis to:
- A title which summarises the content; "client information" isn't very helpful, because the whole page is information for the client.
- What effect the server maintenance will have on the client.
- How the client will know what is going on, when you're actually doing the maintenance.
I've also de-emphasised the phone number, and tried to give it some context about it being a secondary means of communication, after your online updates.