The PayPal unit of eBay has sued the Bank One Corporation, the third-largest issuer of credit cards in the country, charging infringement of a patent for conducting financial transactions over the Internet. PayPal contends its online bill-payment system, patented in 1998, is being wrongly used by the Chicago-based bank. PayPal, based in Mountain View, Calif., seeks a jury trial and unspecified damages in the lawsuit filed Monday in United States District Court in Wilmington, Del. ''Bank One's infringement of the patent has continued unabated'' since PayPal notified the bank's lawyers in February of the reported patent infringement, the lawsuit said. a Bank One spokeswoman, Calmetta Coleman, said, ''We haven't seen the lawsuit and don't comment on pending litigation.'' Shares of Bank One rose 19 cents, to $38.65. Shares of eBay fell $2.01, to $53.64.