Hi,
I hope you are well. I know this was posted in December but I figured I would answer anyway just in case you would still like help with this.
I don't work for Smarty, but I do love the idea of top up vouchers. You could suggest it to Smarty on their socials, or by contacting them here. Personally I would advise suggesting it on socials but the option is there to contact them using the website if preferred. Smarty staff may see this post too and consider your idea.
I understand the frustration of having to use a QR code in a shop to top up your account. Whilst the option of auto renew is there, this of course is not for everyone. What you can also do is through your Smarty dashboard, or mobile app, you could buy an out of plan add-on. This can then be converted to account balance and will automatically apply towards your plan amount. Sometimes I do this, as it's just quicker than going in to a shop, and it gives me the satisfaction of knowing I've paid off my Smarty plan for one or two months.
Please also note that account balance can be used towards purchases of add-ons like chargeable / international calls etc. You just buy it through the website dashboard or app and the account balance applies towards that add-on purchase.
Just a friendly reminder that I don't work for Smarty, but I hope this has been helpful.
Have a lovely week ahead! :)