I have to bitch about this because nearly everyone does this now and then—including many writing professionals—and it’s just sloppy.
‘Free’ is an adjective or an adverb (or a verb under the other definition), but never a noun. That said, you can get something free, you can get something free of charge, you can get something gratis, you can get something for nothing, but you cannot get something for free.
Just drop the extra word, save some breath and say it right. It’s not a ‘buy one, get one for free’ sale, is it?
No, you cannot get ‘some more’ ice cream (‘for free’, as it were). You can get some, or you can get more, but not both together. It’s redundant. Pick the word which expresses what you mean to say and then drop the other. If you’ve had some and you are asking for some yet again, then you are clearly asking for more. Alternately, if you are asking for more, then they know that you want some. You don’t need both words.
Say it slowly. Some more. It doesn’t even sound right. It only even sounds tolerable when you slur in into ‘suh-more’. And we know that’s not right.
We all slip up now and then, but I doubt that most people have even considered these errors.