wrong debit date

South Africa i am sick and tired of i`ve been trying to get hold of them for the past 5 weeks to change my debit date to the 26th and now icant cancel because they will take some of them money if i knew i was gonna go to STANLIB when you wanna cancel there they give you your money the way it is,i tried calling OLD MUTUAL they passing the bug and i am using airtime to call is not a tol free can someone change my debit date i learnt my lessons for my other kids will use STANLIB