Unfair billing and handing over to legal

Im so sick and tired of these ********* called cell c ,i had 3 accounts with them and according to my knowledge i paid off and closed my account with them because of their unfair billing and bad services so now last month i recieved a call stating that one account was not closed so i must pay them i went to their store and one of their consultants at springs mall reassured me that i dont owe them but i just recieved an sms saying that they have handed me to their lawyers. What kind of service is this i never used even one of their sim cards even now i dont because they are ********* and now this????