Any best PC Fax Software solution?

One of my departments receive over 2000 faxes per month on 3 computers through WinFax Pro. 10.02 for record keeping and audit purposes. We have the Analog line programmed such that PC 1 response first and PC 2 response second when PC 1 is busy and so on. However, we have a problem-WinFax does not respond to calls most of the times especially towards the end of the month when call volumes are at peak level. Others call to complain that the Fax line is busy even though the line is not. We reboot the computers every day. Is there any other solutions to this situation?