VODACOM **** TO ME TO BRING MY CREDIT SCORE DOWN

On the first of this month i received a call from Vodacom it was a guy selling Vodacom product (data) , i agreed with him to take it , but now he told me my first payment will be on the 1st of next month , but now am surprised they just sent a debit order looking for money into my account they found no money and it be came unpaid debit order which bring my credit score very low , i wanna ask why ????? are they doing this to me???? , all my life depends on my credit score, i am very disappointed about Vodacom