Vodacom - Account handed over for collection

I received a call from an Attorney saying I owe Vodacom over R 7,000.00. I was shocked. I have not received any communication from Vodacom regarding an outstanding account - not a letter an email or a phone call since 2012 !! A dispute was logged in April 2012 regarding charges that were charged to the account. Vodacom were going to investigate the matter and pass credit to the account. The account was blocked, suspended and cancelled. Now after three years Vodacom have handed the matter over to an Attorney for collection ?