Help with GOIP-4

Dear All, I just purchased a GOIP for personal use. It comes with 4 gsm lines. I would like to use it as stand alone unit without PABX or Astrisks server. I am able to forward VOIP calls to GSM but calls from VOIP to GSM does not work, I get a dial tone all the time for calling from VOIP to GSM but when key in digit on the phone dial tone continues and no ring occur. I keep dialing but straight dial tone continues.

I would appreciate if some one could help me please. Thanks