www.ipkall.com provides free phone numbers in Washington state. The numbers can be forwarded to a SIP address, either through a sip registrar such as Sipphone/Gizmo or directly to your SIP phone.

Note that VoIP calls may not work from Dubai. According to some articles I've read, VoIP in Dubai is blocked by the ISPs. Furthermore, it may be illegal. For more details search google for these terms:
voip Dubai blocked OR illegal