Credit Card Account not closed

In February I paid my credit card account in full and requested it to be closed. To date the credit card has not been closed as i received an sms advising me of balance and that i can use the credit card. I have requested for a paid up letter and have been advised that they are not able to print it and don not know why. I get sms's to pay my account and dont understand as my account has been paid in full.