What is the airtime for a prepaid voucher? SIM airtime is the total number of days you get each time credit is applied to your account. With every top up your airtime refreshes to 60 days. You can dial *120# to check your airtime status. Related articles How to request credit Understanding my bill What is a Recycled Number? How to activate a 4G Add-on? How do you activate a postpaid plan?