That is a known isssue with Hayes modem. You can try this workaround by modifying mdmhayes,inf file:
Before you modify the entries, you should copy and save the original .inf files
with another name or to a different folder. You may want to restore the original
files if this workaround does not work well.
In the [M1806Reg] section, make the following change:
Change: HKR, Init, 2,, "AT&FE0V0W1&C1&D2S95=47<cr>"
To: HKR, Init, 2,, "AT&FE0V0W1&C1&D2S95=47S40=6<cr>"
After these changes are made, remove the modem from the Modems tool in Control
Panel and then re-add the modem. This will write the new .inf settings to the
registry.
This is exctrat from Microsoft Knowledege Base article Number: Q157827