My TomTom doesn't have a sim :-)
I think you'll find it does. Albeit, non-removable. Check in the 'Settings' > 'Connections' > 'Network' section of your unit and you'll see it has a SIM ID and an IMEI.
From the trade review on a Tom Tom Start 60 Europe:
As it’s one of TomTom’s bottom-end satnavs, the Start 60 doesn’t have an integrated SIM card and GPRS modem, and that means no traffic alerts via TomTom HD Traffic. It is possible to add an FM-based TMC receiver for traffic, but this isn’t as comprehensive or accurate .
As you can imagine with me - cheapest is best - bottom end - sums it up or have they lied and sold me a better one than I thought I was getting