So why doesn't it have warranty? There's a million possible solutions, flash a new ROM, factory reset, try installing a different dialer and using that. No offence mate, but you haven't really told us much except only your speaker phone works so you decided to stick a needle in your mic. If it was a software issue before, it could be a hardware issue now.
First thing I'd do is see if it is the dialer that it's stuffing up, try a voice recording app. If this doesn't work, is your phone rooted? If it is, and that's why your warranty is void, you can either try and 'unroot' in a way that makes Samsung think you haven't played with it, or you can try and find the dialer apk, delete (back up) your current one and replace it with a new one. I know there's instructions to do this, on a mobile so I can't find them.
Other than this, as I said, the basic go to's are ROM flash or factory reset. Back up first.
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