Yahoo! Inc and MCI Communications Corp are getting together to offer a Yahoo!-branded Internet dial-up service using MCI’s network and customer service operation. Yahoo! has gathered together so many services through acquisitions and partnerships that it is starting to rival traditional online services, such as America Online Inc and CompuServe Corp, and this deal will probably get some of them worried. MCI already offers a dial-up service, and that remains separate, but the deal with MCI is exclusive, will be called Yahoo! Online and will be powered by MCI Internet. Subscribers to the service will be given a browser geared up to use Yahoo!’s various services, including email, portfolios and search engines. Yahoo! Online will launch a nationwide service later this quarter, though no prices have been set.