Can the spout cover be locked open to prevent whistling?

Hello, yes, just pull the trigger and the spout cover will stay open until you push the trigger back to close it.

Can I turn off the whistle?

Hello, yes, the spout cover can stay on to turn off the whistle.

My kettle can barely be heard, and the company doesn't answer my requests for help . Am I justified in returning it?

I bought a different model from the same company and it discolored so badly I ended up tossing it. If you can still return it, I would.

One reviewer said they didn't think the interior is stainless steel. Is it? Could it possibly be aluminum?

The metal parts of all our tea kettle are made of stainless steel. I apologize for making you have questions about this because we were not aware of this problem at the beginning. We will attach relevant certificates proving that we are using stainless steel in future sales. So that we can completely solve this problem. Thank you for your question, it made us realize our shortcomings. Hope you have confidence in our products and services. Have a good day. VICALINA