The first issue is whether you live or work closer to the county seat than to the court where the ticket was scheduled to be heard. If not, the change of venue statute (
VC 40502(b)) does not apply to you. We do not know whether you qualify or, if you do, whether you documented your qualification to the various officers involved in the issuance of the ticket, or why they changed the venue back to the local court.
If the change of venue does apply to you then, as the court personnel informed you, you may still go to court and assert your rights under the statute. However, they appear to be indicating that once you take action on the file (in your case, seeking and obtaining a continuance) they are unable to administratively change the venue such that you must appear in court to request the change of venue. That may be a limitation of their computer system -- or it may be confusion. Try speaking to a supervisor.
If you choose not to further address the issue of venue with the court, and do not raise any substantive defenses to the ticket, you had best be certain to document that you qualify for a change of venue to the county seat, and should be prepared for the court to take the position that, by filing a TBD without raising or renewing any prior objection to venue with the court, you waived any challenge to the venue.