icelava.net

I've got a server in my company which can be accessed from outside. How do i set the WAN IP to be static as the IP seems to be changing every few days.

How about subscribing to fixed IP address plans for businesses?

Or you can make use of dynamic DNS services to update your DNS hostnames whenever a new IP address is allocated to your WAN connection.

http://www.no-ip.com/
http://www.dyndns.com/

Needless to say there is "down time" between a new IP address allocation and the update interval to the DNS service provider. Whether you can afford this type of service unreliability requires your business calculation.