CentOS server: New ips are not pingable

Hi, I've a CentOs server and my host gave me some new ip's. Usually I add these myself, but somehow I could not do it with my limited linux skills. I've asked someone from vworker to do the job yesterday, but he couldn't do the job. He added the ips with no errors, however they still can't be pinged. So I'm really looking for a experienced guy who can fix this. (Someone told me that this could have something to do with a complete different range? Original ip is 83.220.x.x. The new ips have range 78.47.x.x ) Thanks