hi @Kamille
PM payment system is glitchy sometimes
if your plan not expired or suspended yet and you still have time, please wait a day or even longer before you try again. When you try, try using both Incognito/private/secret mode on your browser and try with Public Mobile app (with Location Permission enabled)
but if your plan has already expired or you need to pay it very soon, then buy a voucher from Shoppers drug mart or gas stations and then load the voucher using *611 or My Account
