What do i do if there's been a credit card fraud?

ok on my credit card bill they were charging me of things that i didn't buy not only was the number huge but believe me am so caution of my credit card i always have it with me so,i called the fraud phone # that my credit card provides me with and they are only taking half of the fraud charges off and i cant pay the other half that is not only a big amount of money but that i didn't even purchased, what do i do?