I am an Indian Citizen and Permanent Resident of Australia. My employer needs to send me to France to complete a project. I applied and successfully received a short stay visa for 15 days. The project dates have now changed outside of this visa validity period. Do I have to a) cancel the current visa an reapply for a new one or b) is there a way I can get the French Consulate in Australia to simply update the dates? Their website does not answer the question and they will not answer the question on the phone or via email. Note: I have NOT left Australia yet.
I'm pretty sure you need to apply to a new visa (and possibly cancel the old one). Schengen Visa Code is pretty clear that:
Filling in the visa sticker
All entries on the visa sticker shall be printed, and no manual changes shall be made to a printed visa sticker.
Visa stickers may be filled in manually only in case of technical force majeure. No changes shall be made to a manually filled in visa sticker.
So your current visa cannot be changed. They have an option to extend your visa (see Article 33), but only for "where the competent authority of a Member State considers that a visa holder has provided proof of force majeure or humanitarian reasons preventing him from leaving the territory of the Member States before the expiry of the period of validity of or the duration of stay authorised by the visa", which is clearly not the case here.