or......
Export your old contacts via bluetooth to your PC (assuming you can) and import to googlemail contacts (assuming you have gmail) then sync on the magic.
I did this and used it as a good opportunity to tidy up my gmail and my phone contacts. Gmail also lets you merge several contact entries to one. For example I had a mobile number for my wife, a home number, a work number, and an email address. I selected all four entries, clicked merge piff-paff-poff......
I appreciate that this post makes a number of assumptions, so apologies in advance if it's of no help!
Cheers,
Iain