How can I order static IP?

Good day,

I understand that basically by default we have dynamic IP in our office, but in practice it's static. But, as I see from other conversations in the forum, it can be changed in theory. 

So, this is critical for us, and we would like to have static IP only (forever) - how can we proceed in this case?

Maybe there are some options on the web-site, but I didn't find it - sorry.