Resignation on my probationary period. Seniors not accepting it.

Dear Sir, I was working in a transport company from past 5 months and i was on probationary. As I was not happy with my work I sent my resignation to my superior giving 7 days notice period which was mentioned in my appointment letter. Now my superiors are not ready to accept my resignation letter nor ready to re leave me. They are trying to make me responsible for those activities which i am not at all related. They want me to take a confirmation from all the customers about the outstanding which was not related to me. Please let me know what i can do now.