WorldNet ISP service is suffering network slowdowns.

For at least a week, users have been experiencing high levels of busy signals, and some have complained that download speeds have slowed. An internal bulletin board dedicated to connectivity problems is being deluged with hundreds of complaints a day about busy signals, from customers ranging from Portland, Oregon, to Ft. Myers, Florida. An AT&T spokeswoman said yesterday that some areas of the system were experiencing heavier-than-usual traffic as a result of the company_s successful advertising campaign. "We are not experiencing the problems that AOL experienced," said Janet Stone, an AT&T spokeswoman. "What we have experienced is that there are hot spots where demand is high." America Online, the world_s largest online service, suffered nationally publicized network congestion problems after offering unlimited use service in late 1996 and early 1997. That episode sparked a number of class-action lawsuits as well as scrutiny by state attorneys general. In an effort to improve its service and quell user complaints, AOL upgraded its facilities and offered refunds to customers. Since launching a new round of television ads in December that tout a new unlimited use pricing system, AT&T_s WorldNet has experienced "significant" traffic growth across its network, Stone said.