Cancel walmart prepaid debit card?

I have a personalized walmart prepaid debit card. What do i do to cancel it? I only needed it to make one purchace online. I noticed the account is in the negatives for the BS fees they charge u every month. Since they have my SS number from when i opened the account, if i just shred up the card and throw it away will i be ok, or am i going to get a bad credit rating since the prepaid card is in the negatives??? its NOT hooked up to a bank account or anything like that, and its only in the negatives for the monthly card fees, not because im buying things and not expecting to pay for them. im not trying to commit fraud or scam or anything, Im just afraid that since they have my social security number this card may lead me to getting bad credit?