I have been using the UTStar UT-304R2U with Grandstream HT486 VOIP adaptor for VOIP calling. However, the Grandstream stopped working last year so I replaced it with OBI 110. Now, for some reason incoming calls are not working. Outgoing calls work great. According to the SIP service I am using the SIP ALG is enabled on the UT-304R2U and it needs to be disabled.

Has anyone had any experience in this? Is there a way to disable SIP ALG on UT-304R2U? Or alternatively switch off NAT on UT-304R2U?