Start Service Request in the HTML form with a Serial #

Good Morning,

We have a need to start Service Request in the HTML form with the Serial #, the issue is once we start the SR with the serial # the Caller can not be added or captured.

The caller being a service technician, dealer and or a company sales rep. These callers are not in a relationship with the "Install Base Owner" nor do we want them to be.  Please advise if there is a way to create tickets starting with serial # and adding the caller next without creating them as a contact.

Thanks