Blue tooth car radios and mobile phones

I hope this advice will help someone.

I have a Sony bluetooth radio in my car which showed me the callers name when I got a call on my Nokia phone. After I bought a new phone the callers names stopped showing, just the callers number, which with all the cold calls flying about is nearly useless, in fact I got scammed twice that way.

I tried to get the new phone (a Samsung) sorted to show the names but to no avail. On advice from Halfords staff I was preparing to buy a new radio for the car but thought that a cheaper alternative might be a new phone. On enquiring the of a replacement phone withTesco 02, the lady advised me that changing my saved numbers from the SIM card to the device (hand set) might work.

After changing the numbers from the Sim card to the hand set I have now got proper caller I.D. I now only answer the named callers, cutting out the cold calls and scammers

So just to confirm:

If your contacts are stored on the SIM card, your car does not display the caller's name.

If your contacts are stored in the Phone's memory, your car does display the caller's name.

Is that correct?

Register your mobile number on tpsonline and the junk calls will stop coming through.

Is it not possible just to switch the telephone off whilst driving? Seems a safer option, hands free or not. Driving on busy roads requires full concentration.