fail to connect to ISP

I’ve been trying to connect to my ISP from RedHat 7.2 to no avail. I have used the same phone number, the same modem, the same username and password etc on Windows installed in the same PC that always work. It dials, connects but drops out while verifying password etc. It comes back with error message saying no carrier detected. At one time, the RedHat dialer says in response to the incoming message not understand but started ppp anyway.

I wonder whether there is anything on the ISP siderequired to be done before I can connect using Linux. I have read all tech info I’ve found and I seem to have done everything I could.