Hi I activated phone for prepaid. I wonder that when i register top-ups for saving 10%, the menu which top-up amount is base plan amount? Amount from $5~ I am confusing. should I select my base plan price? Base plan i chose is $15. If i select $15 on top-up amount, every months I pay just $15+tax by my credit card automatically? Not $15(base plan) + $15(top-ups) , right? Just $15 (base plan) for every months?