PHP Session ID

Hi,

I am completely stuck at the moment. When I try to make a call to the gateway, it works fine the first time, and then all subsequent calls have the phpsessionid appended to the gateway url. Once this happens I can't seem to get the gateway to respond anymore. Drupal just gives a page not found once the PHPSESSID is added. Why is it getting appended to the gateway URL?

Any help would be much appreciated.

Thanks for the work!