First of all, no seat selection is guaranteed. It is annoying if you have a selection, but are still moved. This can happened for a number of reason (seat broken), through bumped for another tier passenger or royalty.
It is also surprisingly common for some people to buy a ticket but not select a seat at the time of booking. The airline is not a mind reader, and would have no idea where you would prefer to be seated. In your case TG has done nothing wrong.
Not wanting to sound critical, but yiu had plenty of opportunity to select a seat yourself. Why did you not select a seat on purchase? Or use manage my booking to select a seat at a later time? Or contact TG in advance of your flight? To repeat, TG did nothing wrong.
In any case, you appear to have a reserved seat for the return. Unless there is some exceptional circumstance, you should be fine. And utterly no point in complaining or fretting over the situatIon outbound as you hadn’t even selected a seat.
Last edited by Thai-Kiwi; Jun 22, 2019 at 12:40 pm