| | Old SIM card worked for me
I moved my SIM card from a 7100g over to the 8700c and all is working fine. I'm not sure what the difference is but if you switch to the new one, you'll probably need to call Cingular and have the account moved to the new chip.
fwiw, I've used the same SIM from my 6210 to 7210 to 7280 to 7290 to 7100g and now the 8700c. It just keeps on working thru the years.