Sounds like the system shows the correct speed of the dialup connection.
115Kbps is the maximum port speed established for the modem and you can
still see it in the modem Properties/Modem tab.
Traditional modem standards assume that both ends of a modem session have an
analog connection to the public switched telephone network (PSTN). Data
signals are converted from digital to analog and back again, limiting
transmission speeds to 33.6Kbps with V.34 modems, and due to limitations of
the PSTN the theoretical maximum is 35Kbps. With V.90 technology a different
assumption is made: that one end of the modem session has a pure-digital
connection to the phone network (which ISPs and corporations already use)
and takes advantage of that high speed digital connection.
V.90 technology is able to accelerate data downstream from the Internet to
your computer at speeds of up to 56Kbps. The data transfer is an
asymmetrical method, so upstream transmissions (mostly keystroke and mouse
commands from your computer to the central site, which require less
bandwidth) continue to flow at the conventional rates of up to 33.6Kbps.
V.92 technology doesn't increase the download speed over V.90, but it does
increase the maximum upload speed to 48Kbps.
Check your telephone line and ask ISP why you get 33.6Kbps connection, maybe
ISP has different phone numbers for 33.6 and 56 connections.