Red Hat Linux 6.0 (Hedwig) was released April 26, 1999 and
was based on Linux 2.2.5-15 kernel.
UMTS only had its very first specification released in 1999.
RF spectrum was allocated/auctioned in 2001 - 2004, only then could actual products appear.
To use Your USB2.0 UMTS "modem"/transceiver device, You should get yourself a much more modern Linux, which actually has driver support for such devices. I would recommend tests with a seperate PC or using a Live Image
System (does not change Your Redhat Linux/does not need a hard disk/SSD at all, boots from a CD, DVD or flash storage). I like Knoppix
for that purpose, You might prefer a Redhat Fedora
I hope this helps.