Unclear billing can come in many forms: it can be as part of a webshop, a clone website, a warning message or a fake invoice that claims to be coming from a trusted and well-known source.
One of the easiest ways of making money is sending false invoices or tricking people into doing online payments for software or services under false pretentions, like upcoming extra costs or fines, termination of privileges, unclear terms and conditions etc.
Ofcourse there's no software against this type of malicious activities, one should be very careful when payments are requested by message, e-mail or pop-up screen etc. and always double-check the claim by visiting the official website from a trusted bookmark, application or search-query.
Unexpected and/or harmful downloads
Unexpected and/or harmful downloads belong to a category of malicious activities that typically tries to trick a person into downloading a file or software through messaging or online redirecting, giving misleading information in combination with supplying a link or hiding a link in an advertisement, an embedded video etc. Some websites even contain malware that installs itself on your device only by opening that website in your browser (drive-by attack). We see all kinds of techniques here like phishing, URL-redirecting, including Trojans in downloadable applications etc.
Staying alert and having good anti-malware protection are primairy ways to keep unwanted downloads away from your device.