NEW YORK: Hundreds of America Online subscribers unexpectedly received bills as high as $500 last month after using a special AOL 800 number in order to circumvent the busy signals which have plagued the network since the introduction of its flat-rate plan in December. The line was set up for users in remote areas that have no local dialup access. Subscribers who learned about the special access line from AOL marketing personnel were warned that they would be charged special usage fees of $6 per hour. But once news of the number hit bulletin boards and chat rooms on the service, legions of frustrated subscribers started dialing in without realizing they were running up big bills, assuming that being an 800 number, it would be free. Some AOL members didn't have a choice but to connect to the network through the 800 number. According to representatives at computermaker Packard Bell NEC, thousands of computers were shipped this winter with flawed software which automatically routed users through the access line. Although these people will receive refunds from AOL, the other surprised subscribers may not be so lucky: a spokesman for the company said today it will examine each refund request by this group on a case by case basis.