I own a Teltonika FMB120, so how is it programmed by SMS? I'm trying to program the device through messages, and I'm not aware of that.
Providing you have the physical device to hand, you can use their Configurator software to set the parameters for the reporting etc.
Remotely they do have an API (of sorts), using their Parameter List (FMB series, Codec dependent too. You can find which Codec is being used in the Header after you perform the initial handshake).
the API for remote configuring is painful to say the least.