tabs on user pages

Hi,
I still can't figure out how to edit cc_custom.module to be able to remove tabs and edit tab titles on the user pages.
I've tried adding this to cc_custom_menu_alter()

unset($items['user/%/balance_history'];
menu_rebuild();

and cant get any changes from that. Even if I delete the menu items as they are declared in transactions_menu() in transactions.module (which I know is not a good idea), the balance history tab still shows up.
I've tried running menu_rebuild() straight after my new code, and also from a separate page, but this doesn't make any difference..
thanks for your help,
Rachel