If someone comes across this page - I must give you warning!
Most OTA follow the DOT rules given to the airlines - each customer booking with a US travel point (domestic or international) has the right to cancel for FULL refund within 24 hrs of booking a reservation. All US carriers honor this and most OTA (Orbitz, Priceline, Expedia, Travelocity, CheapoAir, etc. etc.) follow to avoid losing business to direct airline books so they offer no fee changes/cancellations within 24 hrs if you change your mind.
Vayama - charged me $50 to cancel a reservation within the 24 hr period. Here is the insanity of it - they charged me $10 service fee for my ticket and the remainder was direct to the airline according to the confirmation invoice . Upon call within 24 hrs to cancel (changed my return date) - Vayama said they would refund me everything except $50. So, I haven't seen the charge yet but I anticipate they will charge me $40 additional dollars for a transaction they never submitted to the airline as I bought the ticket on Sunday evening and they have time to void (without processing).
Anyway, avoid this OTA even if cheaper as I have used them in the past but NEVER NEVER again. Go direct to airline or use alternate OTA competitors.