[USR-TC] Quad to DSP problem

Several days ago I have changed my analog phone lines to an E1 (was connected to Quads, now to HDSPs TCS4.5). Some users were connecting to analog TC using their mobile phones like Siemens SL45 (with internal modem). This is written in SL45's manual (for modem): Modem driver: Conforms to the V.25 command set. Speed: Conforms to ITU-T standard V.22bis (2400, 4800 and 9600 bit/s). Now my problem is that this users cant connect to digital TC. How can I set up this protocols on DSPs? Thanks, alex.