I don't see any problem whatsoever, I get TG and other airlines to change tickets all the time, sometimes there is a fee, most times if C or F there is not. The only problem could be if the ticket is a new 30day release, with no stop overs, but I am thinking yours might be an award ticket. If it is TG stock there is no problem, if it is another carrier, you might be wise ti check them too.