I'm flying LGA-ATL-HND / HND-MSP-LGA in September.

I'm trying to get an MUA to Delta One from Premium Select (G), but the agent said my fare isn't eligible? Is that correct? I've seen it elsewhere on the site that I should be eligible, and yet I can't do it. I've tried everything in the guide, but they keep saying I needed a higher fare class.

I'm wondering if the fact that I have domestic connecting flights is the issue. I only care about the MUA for the international flights, so is it possible I can it upgraded just for those?

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EDIT: I got connected with the right agent via chat and I got the MUA! If anyone else sees this, just be persistent. It took me quite a few tries.