Default Proximus Belgium 4G 1800Mhz

Hello,

I'm trying to activate 4G on my Droid 4, but it seems that I can't get it to work.
- Stock ROM (with build.prop changes from Mentor)
- CM 10.1.3 (with Mentor's gsm patch)

Proximus uses 1800Mhz band for 4G / LTE according to this article
http://en.wikipedia.org/wiki/Proximus

Does someone know how to enable 4G on my phone?

TIA,
Fossie