Try to have my Sim application processed

I have been trying to pay for a Sim the customer zone allows for a credit card payment for instant payment.i gave with great difficulty managed to use my debit card details. The person that attempted to assist arranges for a debit to be processed from my savings and this seems to want to go of a credit card that does not exist can someone assist me the WhatsApp is not helpful to me kind Regards Lenny Chetty