Is "don" really right in that context? Wouldn't that mean "on behalf of Christmas?

I don't think don Nollaig is the correct way to translate the English "for Christmas" as usually intended. To me the sentence reads like "I got a new phone to give to Christmas" not "I was given a new phone for Christmas." The FGB has i gcomhair na Nollag to mean "for Christmas" but unfortunately doesn't give a full sentence. It seems like this better captures the English idiom but I'll admit I'm not 100% certain. The absence of a lexical equivalence between "for" and any single Irish preposition continues to vex me.