Some phone service providers, notably T-Mobile and Verizon, offer a service that sends voicemails as texts. You may get a message that says a voicemail was deposited as a text and then a text message ...
Text messaging has long served as a quick and convenient alternative to making traditional phone calls, but in certain situations, there are some messages that can't really be conveyed without audio.
To switch off call screening, open the Settings app and head to Apps > Phone. Scroll down to the Screen Unknown Callers ...