Good luck with retentions, there will be a few that will try it, but go check your contract for the statements on availability/uptime. I bet you dont have any SLA attached to it, so they'll just wave you good bye.
I feel for people that lose business when phone networks go down, but really there's nothing you can do about it other than to have a landline and a mobile for a business. At the end of the day its the same as when a car breaks. You just have to try and get it fixed ASAP, its not always the manufacturers fault, sometimes things just fail. My understanding of the O2 problem was they didnt know what was causing it which makes it much harder to find. Its not like all customers in London suddenly went down. There appeared to be no common denominator which working in IT makes it a ball ache and a half to try and trace it