Hacker???

I fired a guy who has a conviction for getting into the computers of a computer company and stealing $25K. Now I think he has invaded my computers but everyone just says I am nuts. I see files being moved or disappearing, access logs in the Administrative Tools being overwritten, my IPhone was hacked (the Genuses said the term was Jailbroken), and other things I don't understand. If so, we are now installing some type of system with statice IP addresses and a server that I am told will prevent any access, but despite it going in yesterday, today I still see things that look odd to me. There is an email from Microsoft asking me to verify a Windows Live account, which I did not set up and they say they cannot confirm with my phone number or the email they sent the request too, for example. What to do?