What is the airtime for a prepaid top-up? In this article Sim airtime is the total number of days you get each time credit is applied to your account. With every top up, your airtime resets to 120 days. You can dial *120# to check your airtime status. Related articles How much am I paying to make calls? How can I check my balance? What is your bonus credit? Why can't you see your credit after you Top Up? How to top up with a voucher card