Welcome to the group.
I think you will regret going back to the cult....for any reason.
But, if you insist, write a dated letter outlining WHY you wish to return. Document you are no longer "living a life of sin". :) Document what you have done as to "Works befitting repentance" (I apologized, read the Bible, prayed, returned $$, sent cards, attended x number of meetings...in person..online, etc., talked to co-workers, yadda.. yadda, etc., etc.) Send a letter every month or two for 6 months.... if you can stomach it.