If you pass the echo test (*600 or 600), can make calls to your Voxalot account from another SIP account or from a SipBroker access number, and can establish reliable 2-way audio, then it should be relatively easy to point the DIDWW number to your Voxalot account - sip:xxxxxx@voxalot.com or just
xxxxxx@voxalot.com
I am not familiar with the workings of their interface once you sign up for a number.
Make sure you select SIP protocol, and pick which server you prefer to use (USA or Middle East).
Did you try their test number on their "Try Now" page pointing to your Voxalot account:
DID World Wide, International DIDs forwarded to PSTN and VoIP by SIP, IAX, H323, Skype, Gtalk, MSN Messenger. Origination services, SIP DIDs
If the two way audio tests indicated above are not working, then the problem may not be caused by the DID from DIDWW.