It is simply because there are secret installation (malfare).
Quote
"You have all these wonderful features for cheap, but there is a hidden cost,” he told BuzzFeed News. “There are a lot of Chinese phones that have malware installed on it.”
Quote
Mxolosi’s Tecno W2 was infected with xHelper and Triada, malware that secretly downloaded apps and attempted to subscribe him to paid services without his knowledge.
They are installed on your phones especially phones from China that comes cheap in your eyes lol , but you pay from the other side 
through unsolicited data consumption. Quote
Typically, malware like Triada and xHelper requires someone to be tricked into installing it on their phones, rather than it coming straight from the factory. It’s often used to deliver invasive ads that send money back to whoever controls the malware. But it can also be used to install apps that subscribe the victim to paid services via monthly billing or prepaid data — siphoning cash directly from the phone’s owner.
And this happens to any user of the phone despite your country because the word colonization wrongly gets people to focus on third world countries, no. This is digital colonialism.
I find this helpful and you can read
https://www.buzzfeednews.com/amphtml/craigsilverman/cheap-chinese-smartphones-malware