Like OP, I stumbled here after failing to find a phone number on the VT website. It does appear to be missing on purpose. "Contact Us" page has an online form.
I was going to inquire about changes/cancellation, which seems generous if a little ambiguous. No fee for a change that requires no "fare change", it says. And ~$25 USD per flight if "fare change". I was going to inquire what constitutes "fare change". I'm assuming it means fare
type. If I change from high season to low season, is that a fare change? How about 20kg bag allowance (Y) to 50kg (Z)? Appreciate any knowledge.