Capital One Credit Card Complaint

Capital One Credit card department,

Transaction issue Florida

After my small business failed the only option I had for a credit card for my new business was a secured card through Capital One. I signed up for this account, deposited $2800.00 do bring my available credit line to the maximum $3000.00 limit. My complaint is based on a recent transaction that was declined because I was three days late on my payment. There are plenty of funds on my account to cover this transaction. I have a payment scheduled for this account today three days passed by due date and yet they still decline my transaction. I feel that this is an unjust practice considering that I have available secured funds and that I 'm only three days past my due date - can somebody please tell me if this is an acceptable business practice?