contract expired and im still being charged

I called cell c last year 2014 in September asked them to block my simcard as its has gone missing and I no longer use it. contract on the sim card ended in Juanuary and from february cell c started debiting me more than usual , when I called to find out ther said this is because my contract has expired , asked them why could their not cancell it their said ,i was suppose to call and ask them to deactivate it .<br> if i ask them how I was suppose to know that my contract ended their told me that their sent me a text message on the simcard that was blocked. and i asked them how was i suppose to get the message if simacrd was blocked? asked them why their did not use my other numbers that i have working with cell c?<br> I could not get an answer.<br> in march their debited about R550 and this month their did the same for a number that is no longe valid. this is unfair as their have the nu,ber on the system as blocked but their still debitting me even though contract has expire.