You’re SIM card is not high enough to make any purchases

You’re simcard balance is not high enough to make any purchases please increase you balance and provide a new payment

so when ever I’m tryna buy an app from AppStore There’s something kept popping out on my screen whenever I buying an app from AppStore it said “Add a new payment method” you’re prepaid balance is to low to make any purchases” but I have enough balance to make any purchase

pls help