Did your phone connected to same network as your computer, like using wifi?
Or if you use mobile data, does the mobile data come from same company that provides your cable connection?
If that the case, probably your ISP has some kind of caching (maybe to provide better internet experience for their customers). All you can do is to wait for their cache to be expired and they will fetch new one.
Because, it also happened to me and my ISP in rhe past. They cache a lot of internet content, and cause me quite a lot of headache when update/download software updates, because I always got the old version from their caching servers.
The page you saw is the domain parking page we use for all unused subdomains. The parking page is automatically and (almost) instantly removed when you add the domain to an account, but it may take a while for the domain to start working everywhere.
The domain parking page is setup on the DNS level. That means it’s subjected to DNS caching, not web page caching. DNS caching can be done on your computer, on your local network or at your ISP. Clearing browser cache tends to not work to fix that. What does work is explained in the article that @anon19508339 shared above.