If the goods were bought in Switzerland, you can get the VAT form stamped by the Customs officier at Geneva mainstation (Gare Cornavin).
Their office is on your way to the platform for the TGV. However they will not refund the VAT. They will stamp the form and then you mail it into the address given on the form. Money will be refunded to your credit card.
Just don’t expect much. VAT in Switzerland is only 8%.
To get it stamped:
Before you go to the TGV platform (track ⅞), you will enter an area that states you can only pass if you have a ticket.
Go through it and at the area where they do random checks on luggages & people, on the right hand side, there is a tiny passage and sign that points out you should enter that door for Swiss customs for tax purposes.
You can get the stamps there and mail out your forms.
You have to leave the country immediately once you got the forms stamped.