[Serusers] SIP Gateway

Hello, We are trying to find a SIP to SIP gateway and we fell across this project. Can someone tell me if we can accomplish the following with this software. 1) Our DID/SIP telephone provider does not support the Refer method, and as a result our SipX IP PBX can not transfer calls from extension to extension. 2) As a work around we are thinking that we could install a gateway between the DID provider and SipX where the gateway would support the Refer method and handle the transfers. This method is not ideal because all phone traffic would need to go through the gateway as opposed to a direct connection between the DID/SIP provider and the end user extension, but we can't see any other solution. So, can Ser act as a gateway as needed, or is there another solution that anyone of you can think of. Thanks DB