Register to a netwrok

Hi all,
i would like to get some help.
i have a device connected with a roaming SIM
in the area am in i have 2 cell networks that i can connect to, one of those networks is much better then the second one.
when i turn the device and try to connect to a network, must of the times it connects to the weaker network.
and there for my question.
1.on my first turn on how can i make it connect to the network with the best reception?
2.If there is any way to choose the network that am trying to connect?
3.if i already connected to the network with low reception can i change it to the better one?

Your question is not clear. Please let us know which Seeedstudio product you are using.