wich GSM shield must I buy

I buy a official GSM shield and it seems not working.
I can but an other one, but I don't know wich one to choose:

  • An official Arduino shield with Quectel M10 modem
    [li An SIM 900 shield][/li][/list]
    [li an SIM 908 shield][/li][/list]
    [liAn other modem shield][/li]

What I need:
First I need to have a socket to send data over internet in a POST request.
Second if possible I need UDP socket for a NTP query.
Third I need a server socket all the time open

And may be SMS send and receive.

Many thanks for your help very appreciate.

Best regards

Thierry Vorms