I created a callbox bot using Twilio about 10 years ago. It started as something simple: when my callbox bot is called, play dial tone 9 (to signal the callbox to open the door) and then send me a text message that someone is coming up. I wasn't too worried about people abusing the system and this worked really well.
Over the years, I've made it more complex. I added a simple menu system using text-to-speech and accepting the DTMF tones for the selection. This way I could tell people to enter a secret PIN and they could provision themselves access to my lobby. If they didn't know the secret PIN, there was an option to have it patch through to my phone so I could screen the guest using normal voice and I could manually press 9 on my cell phone.
It also has an SMS interface where I can select different modes and hours of operations. So when I host a poker night, I'd txt my bot "poker" and it would it update the menu system to be Poker themed so that when guests were at the callbox they'd be greeted with poker puns. When my friend comes to visit from Austin, I'd txt "StarCraft" and he'd get to hear some dumb SC2 puns. I have 20+ different modes now for various occasions over the years. Now when people visit they get their phones out and record the greeting half-expecting something that they would want to remember or share on social media.
Sadly, my building just replaced their callbox with a newer model that does not accept secondary input. So once the call is connected to Twilio, if the user touches any button on the callbox (e.g. to enter a secret PIN), it will disconnect the call. I suppose it's now time to use some voice-to-text options to bring back the interactivity, but I suspect the lag would make the experience more frustrating than fun.