If an Organization Have A Category External Auditors, So do you recommend them still to have internal audit annually?

extremely for a very simple reason, whatever the external auditor you deal with him you are a client, a client flow cash, on some points they would be nice and easy and letting it go to just keep everyone happy and keep there contract cause you are a client, the internal auditor has the company allegiance, he is an employee, he get a salary to pick things up, so he will try to find anything which will make him more persistent and strict more than the contract external audit firm, you know, you are a chief accountant, by the end you have the meeting with your company profile senior external auditor and agree which he should put and where, and i'm talking about the big four :D

Though external auditors are experts in their profession--their approach to many issues are different. It is better to have your own internal auditors who can care and specialize in your own business and activities and their presence will bring additional security dimensions to the org and more internal control at lesser expensive than professional payments. The internal and external audit by two separate teams will highlight more of the take care areas concentrating on each other focus areas and strengthen the audit process and it merits.