Stop putting QR code on your posters in the city.
I don’t have my phone with me.
When I have it, I don’t want to open it.
When it is open, I don’t want to scan random stuff.
Just put the information on the posters. The date, the place, the price. Write them !
Add an URL to your website. One I could memorize, note down or even recognize later.
And no instagram/facebook. I want the information, not "follow".
You are not cool, you are simply losing a huge part of your potential audience.