Just sharing an old idea.
User Manager Account Renewal with SMS using KANNEL/playSMS
mt - code found.png
Please note that I took User Manager as an example and uses some low and un secure scripting method. (I have no experience in creating good scripts either in linux or mikrotik, so LOT of room for improvement I know). The goal was to demonstrate the capabilities (of mikrotik and playSMS ) and things we can do by combining various apps and cross platform OS to get our results. This is no way a perfect example, but I am sure it will give you some idea how things can be started : )
You can take this example , and you can generate you scratch card codes and store it in MYSQL DB and FREERADIUS, therefore you can then pull CODE from specific DB and act accordingly after receiving SMS. I am sharing just some thoughts : )
https://aacable.wordpress.com/2015/05/12/sharing-ideas-mikrotik-with-kannelplaysms/