Dial-up speed problem

When dealing with modems there are two different link speeds that the AT command set recognizes: the speed of the link from the computer to the modem, and the speed of the link from the modem to your ISP's modem. Because it's physically impossible for a modem to connect to another modem over the telephone line at anything higher than 56K, the 115,200bps figure has to be the speed of the link from the modem to the computer - not the speed of the USB connection (obvously that's faster) but the speed of whatever layer of legacy protocol junk the modem uses.

In other words your modem never connected to the internet at 115,200 bps. If it connects at only 40,000 bps now, it probably always did, but you never saw that it did because your modem init string told the modem to report its modem-to-computer link speed instead of modem-to-modem link speed. Probably it's better now, because now you know the REAL speed the modem is connecting to the internet at.