has been crippled on the 5185i by requiring that the sublock code
be entered after selecting Alpha Tag.
If you do manage to find your sublock code by some way or another, enter that at the prompt. A screen will then be shown with the prompt "Alpha tag:" and the sublock code in the box. Hit OK, and an "Accepted" screen will appear, then drop you back to the Alpha Tag menu entry, which will still display your old tag. Hit Select now, and the "Alpha tag:" prompt will reappear, with your old tag displayed in the box. Anything you type now will erase the old tag.
Hit OK to save your changes, power off, then power on. Voila.