communication between PLC M340 (RTU NOR200h) by GSM

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comunication between PLC M340 by GSM using RTU module BMXNOR200h
(extern modem GSM SR2MOD02)
the modem is connected to the serial port of RTU module, so how can'i communicate with the modem to make data call?
there is some functions in Unity Pro?
thanx a lot