For me, I find it impossible to use Free Coupon with entering any payment card information. Any ways to use Free Coupon with entering card information? Thanks
Google's assumption is that you're opening a new account and will want your ads to run continuously when the free trial is up, so they do require you to enter a payment method. If you don't want to spend more than the value of the voucher, you can stop the ads when that's reached and you won't pay more, but you do have to give some kind of payment method details to start with.