no dialtone on SONY Laptop internalmodem

I get a response from modem but no dialtone when trying to dial into network. Sony website has a couple of fix but it is still not working. This is the third sony laptop that this has happened. If i used external or pcmcia modem it is fine.
Does anyone has any suggestions. It is currently using COM3, with ATX0 in the advanced string. and wait for dialtone disabled as suggested by SONY. I have also tried COM2,4
Thanks