I sent bitcoin to an exchange using an address I had used with them previously, but then found out that they had just retired/stopped using that address. They said I should ask from them the right address every time.
I saw my transaction ...
Bitcoin.com is just one domain name used to promote Bitcoin. Bitcoin.com is not an official website. Just like nobody owns the email technology, nobody owns the Bitcoin network.
As such, nobody can speak with authority in the name of Bitcoin.