My upgrade disappeared.

A week ago, both iPhones on my account were eligible for upgrades. My son upgraded his iPhone 6 to an IPhone 7 plus using the Next program. Now my upgrade eligibility information panel says both phones are under the Next plan and that my iPhone 6 is not eligible for an upgrade until September of 2018. I wanted to use the Next plan for my upgrade too, but now it appears I'm stuck with an iPhone 6 for another two years. Is there any way to restore my upgrade for my second phone?