1) If you don't have a Sonic subscription, you can get a Sonic subscription for the length of the Knux issues they owe you.
2) If you have a Sonic subscription, you can extend it by the number of Knux issues they owe you.
3) You can get back issues of Sonic, Knuckles, SSS, or Nights that equal the number of Knux issues that they owe you.
4) You can subscribe to Archie's comics, such as Archie, Betty, etc.
5) You can get a refund that is the number of issues they owe you times $1.25
Those are the choices.