The name for champagne is "champagne".
I mention this because when you call champagne from California "champagne", somebody is going to jump down your throat and insist "no, it's sparkling wine -- champagne only comes from the Champagne region in France". They are wrong.
This seems well sourced and presents a more nuanced view:
https://en.wikipedia.org/wiki/Champagne#Use_of_the_word_Champagne
While the term champagne can be legally used in the USA to refer to some sparkling wines that had the right to use those labels before 2006, new wines may not use the term. Over 70 countries put legal restrictions on the term.
So, both of you would be right, in some ways.
But, it is kind of like calling this Bourbon:
https://thewhiskeyjug.com/swiss-whisky/whats-the-deal-with-macardo-swiss-bourbon-whisky/
