Checking operation of a cellular module on an operator network

Hello All,

I hope this is the right place where i can present my problem as i need a help :confused: .

Is there any thing that truly makes a cellular module operates on an operator network not on another, knowing that the cellular module supports both the bands that the two networks operate on??!!

Thank you

Signal level? Most likely.
Enabling bands? less likely.

What modem?
What bands?

How, exactly, did you test this?