Delete network interface in AWS

Job ID: 34754601

Budget: ₹600 – ₹1,500 INR

I am not able to delete 3 network interfaces in my AWS account.
The description of all the 3 interfaces looks like "AWS Lambda VPC ENI-ReadEmailContent-a6eb99b4-722d-40b6-8d5c-d6843f473d26"
The AWS Lambda function in question has already been deleted but still the network interface appears to be in use and not allowing to delete.

Can you give me exact steps to delete these interfaces?