When I receive an internal call from the clients regarding a service request or a complaint how to answer the call from the help desk and to end the call.

I would answer the call exactly the same regardless of where it comes from, this shows uniformity and proffesionalism;

To start the call;
"Good morning / afternoon, corporate services helpdesk, (Full Name), how may I help?

To end it;
(Give out any call references needed) then, once you are both satisfied the conversation is over "Thank you for your call, have a good day"

I prefer my approach.
"What do you want !" or "What have you broken now !"
And
"Have you tried rebooting ??"

Works a treat, that and the 20 min rule ;)
Do nowt for 20 minutes after the call and if they do call back then do something.
Most of the time it's a PEBKBAC error or an ID TEN T issue.

Ha ha, so harsh... but fair - Layer 8 snags seem to be the most common!

I once had to describe to a female caller where to find the 'Shift' key was!
I don't think people that dumb should be allowed a computer!

"Have you tried turning it off and back on again" is always a good option!

When i receive an internal call from the clients regarding a service request or a complaint how to answer the call from the help desk and to end the call.
State the company's name, your name and how may I help you?