Is antenna required with Arduino 3G/GPRS shield?

I am working with arduino uno rev 3 and arduino 3G/GPRS shield. i have uploaded the code for sending sms through the shield to my mobile. The message has reached up to the shield and it is seen on the serial monitor but it has not reached to the mobile.

i have purchased both the boards from cooking hacks, the GPRS shield is with audio video kit but GPRS antenna is not included so my question is--
can i do this without antenna? Or can I use any other antenna Or can I fabricate my own antenna?

As buying a new antenna is a very time consuming process as it takes 20-25 days for shipment to reach and my exams are due so I want to complete my project as early as possible.

Thanks.