how do I permanently disable the loud speaker function for phone calls on my iPhone?

or the speaker function flicking on at random is a design fault which you yourself have acknowledged, necessitating my question (FYI, I didn't ask any questions about the proximity sensor, if you re-read my question, I asked if it was possible to disable the speaker function).

You "acknowledged no such thing"?

Once again, I must have been imagining it when you wrote in your post: "I know it is the proximity sensor in many cases".

You're the person who confused my information about a faulty proximity sensor with being the purpose of my original post (FYI, again, it wasn't).

But I am glad that you're no longer following "this strange thread".

Good luck.

It's a pity that the speaker function on an iPhone can't be disabled, while I've got my phone settings set as you've suggested, the problem stays the same with the phone - my iphone's touch screen is faulty & activating inappropriately (for example, activating other functions after the Lock Screen has been enabled).

Checking that "the speaker icon is not illuminated before putting the phone to my ear" is actually a rather stupid comment; touch screen is faulty and activating incorrectly. Yesterday when I took a call, the speaker function flicked on as I put the phone to my ear - I know this because as you suggest, I keep an eye on the screen for this very problem.

I've had this iPhone replaced once already because of this problem (and I've had this problem of the speaker function becoming enabled at random during a phone call).

Yeah, so I must have been imagining it when I had the tech at the apple Genius Bar tell me that it's happened to him too & he's known of a few other iPhones with this speaker phone problem (it's caused by a fault in the proximity reader, FYI).

Cheers

[Edited by Moderator]