Hi, QBZappy.
You recommended me to disable SIP ALG on my router. My router is Dlink DVA-G3810BN/TL which provided by Telus. I can't find where to disable SIP ALG because Telus blocked the SIP setup on this router. I downloaded the DVA-G3810BN manual from Dlink, this router provides how to disable ALG. Who knew to disable SIP ALG? please tell me. Thank you!