Maybe following the procedure mentioned by Flaps50, as if it cost more, is the answer.

If the ticket is less you book it coach which is probably even less, then submit the online upgrade form to GTravel (they get it as soon as you submit it, you can do it on the phone with them even). Then they ticket it if the amount you were willing to pay is more or equal to the upgrade cost.

I have never had a problem booking 1st class through Global Travel when the fare is cheaper than coach!

I think his problem is it is not cheaper than coach on the route he is flying while it is cheaper than the coach accepted fare.

Copy. Thank you.