Rippe off

I recently lost my job to which i owed Cellc R3657.94 in my Oct statement. of which my number has been barred for outgoing calls and the data plan is also switched off. today 13 Dec Cellc sent a statement of me now owing them R6080. How when my contract has expired and my minutes were switched off and couldn't call out or text or use data. How must i pay for a service i am not using because my contract expired end July. and had asked to just keep me minutes.