Investigation: our phones ARE listening to us

It's a question I've been asking for a while after seeing adverts for things I've been talking about - but not searching - popping up on my phone.

While we are all used to targeted ads - seeing pictures of things we've just searched for appearing in ad spaces on the websites we visit after - many people think advertisers and phone companies are taking this one step further.

If voice recognition apps like Siri and Bixby are always listening for commands, is it really beyond the realm of possibility that they are also sending ads our way based on what we're talking about?

While tech giants including Facebook and Apple vehemently deny they are using phones to listen into customers' conversations and then sell the data onto advertisers, I wasn't so sure I believed them.