Flighttrotters.ca and/or Flighttrotters.co.uk is a scam. They post very low fares for a flight to entice you to book with them. Once you have booked, they call you with some ridiculous story and asking for an additional amount. In my case, it was over $1000. I refused and asked that they reimburse my payment as per their Terms & Conditions. They obviously refused. I am working with my credit card to recover my money.
Avoid this company by all means.