When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Sorry, I was talking about my iPhone. No idea how the android phones work.
That's a setting called "WiFi Assist" that can be enabled in the settings menu. It was the subject of a few news articles awhile back for causing people to unwittingly rack up data usage charges when they thought they were on WiFi. In recent years this has become less of an issue with the prevalence of unlimited data plans.
Good call with the date though, this wasn't something iPhones used to do.