How can I set band for SMS

Dear all,

I am traing to send SMS.
I red this:

Make sure the proper GSM band has been selected for your country. For the US the band must be set to 7.
To set the band, use this command: AT+SBAND=7

As, I am not in US, how can I know the band for other country?
For now I need for Switzerland.

But there is a lits of countries?

Thank a lot

Here should be the answer