@Royce Renzo Galeos Thank you for reaching out to Microsoft Q&A. I understand that you are having issues with deleting your Public IP even after deleting the NIC that it was associated to.
This issue may require internal investigation into your resources. If you have an Azure Support Plan, please do reach out to them so they can look into the same. If you do not have a support plan, please send mail to AzCommunity [at] microsoft dot com with subject: "ATTN: Sai Kishor" include your Azure subscription ID and a link to this forum thread (for context). We would like to enable one time free technical support on your subscription to put you through Azure backup technical support team to get quick resolution to your issue.