Default [Q] How to unlock phone for 4G

Hi All,

I have a HTC One from Three in UK. They have started rolling out 4G network in London in December and I live in good coverage area.

I got a text from them that they are rolling it out and that I need a new phone or software update on existing one and to check their website.

Well HTC One is one of those phones that needs software update to have 4G.

I also know that my phone is 4G capable as there was a thread about how to check it a while back but I cannot find it now.

Any help on how to unlock it for 4G?

I do not want to relock the device to go back to stock just to do that. Especially that I am now S-off and all that.

HTC One in Silver.
Nexus 7 WiFi (1st Gen)
HTC 8x in yellow as I still think windows phone is a better day to day phone.
HTC HD7 as no one wanted to buy it.
Reacquired my old love HTC HD2.

R.I.P "Super Sic" we will remember you.