While I do suspect they listen, I have pretty solid (anecdotal) evidence they scan text messages. When I bought my house I had no solicitor, I text my buddy to see who he used and he texted me a response.

Started to type into Google to get a number and it was the top suggested search after 2 chars. Nowhere else did I mention this solicitor, hadn’t heard of them before this, have no other searches for this solicitor. It’s not a big firm, it’s not even in my city - only explanation I have is they scanned the messages.