hi,
What is understand is your webdispatcher is exposed to internet. and your webdispathcer is connected to backend abap server.
Now you want to access services in abap system through webdispatcher. but while accesing these services from webdispatcher you are getting abap server hostname in addressbar.
If this is the case then can you check httpurlloc entry in abap system is it having public hostname .i.e. webdispatcher details the address which you use from internet.
Regards,
Rajeev