Depending on what you want your project to do, you don't need to connect a phone number to a SIM card. Twilio does that for you, letting you use their API to s

Depending on what you want your project to do, you don't need to connect a phone number to a SIM card. Twilio does that for you, letting you use their API to send and receive SMS (text) messages with other phone numbers. It's the recipient's phone number, not your Twilio one, that's connected to a SIM card. What the linked post here talks about is using a device that's basically a mobile phone in a USB stick form factor to send and receive SMS like you'd do on a mobile phone. You buy a SIM, insert it into the device, and start texting. That's the other side of what your Twilio project would do.