GSM modem reconnect issues

Hi,
I have a Wavecom M1306B gsm modem and am having difficulty with its
roaming settings. It is connected to a node however when the
connection is lost the modem will not attempt to reconnect to the
network. To get the modem to work again the SIM has to be removed and
inserted into a mobile phone to initialize it. I have looked at the AT
commands for the modem but have only found the

AT+CREG=<mode>

command. Is this relevant to what I wish to achieve?

This is a "second hand" project given to me to improve and I am
completely new to GSM modems, AT commands etc and any help would be
greatly appreciated.

Mark