Haven't received the Credit Card but already owing

Sales person from standard bank phoned and i took the credit card and i agreed that in reception of a credit card i will pay R116 then i will be given a credit card to my surprise i have not received a credit card but i received a letter wish says i am owing R539.28 and on the 10th of march i went to horizon view standard bank to cancel and i requested them to cancel and reverse all monies due and i was promise that they will cancel the card at card division.On 14 April 2015 i received a letter wish says i must pay the total amount due of R100 and they said amount payable may include permitted default charges and cost incurred by them to enforce the agreement up to date and i must respond within 10 days ,on 15 April i paid thr R100 and on 29 April i received an sms to say i must pay R25 and the balance is R499.48. i am shocked that i did not cancel but busy billing me.