I have a Telstra phone that will not download my phone address book but have a 3G phone that will. I did this once and had a look to see how it stores them. with your Tomtom connected to your computer have a look at the directory structure through explorer. You will find that it stores the address book in a folder called CONTACTS and as a text file that can be edited in any text software such as windows notepad. It needs to be structured like this including quotes: "Tom Roberts","039786853","HOME"
The home will tell your Tomtom to use the Home Icon against this entry. The other icon names are: CELL and WORK. I downloaded my address book from Microsoft Outlook, tidied it up in Microsoft Excel then wrote a function to concatenate the name, phone number and type into one line then copied and pasted it into notepad and saved it in my Tomtom directory called contacts overwriting the file already there. Be aware Tomtom is very fussy about the exact spelling of it's files.