I'm flying with my 3yo daughter on Thursday YYZ-DEN, this is a 220. Booked as a UA codeshare number, operated by AC (I'm connecting to UA). I had requested seat assignments so we could be sure we would sit together, and we were assigned seats 17AC. Last time I checked, a couple - a few days ago, we were still in those seats. Today, I checked the reservation, and we were moved all the way back to 36DE - this despite the fact that there are several empty seats forward of the exit row (including the seats we used to have), as well as every seat in every row from 26 back. Is this normal?

I tried to change seats myself online, and am being given an error. Seats are also showing at a cost, which I understand is not supposed to happen with a young child, but also, even if I want to pay, I can't, since it errs out when I try.

I did send a twitter DM to see if they could sort this out (they have with seating issues in the past), and on the good side, they replied in like 10 minutes. Unfortunately their response doesn't make any sense. They told me that passengers traveling with children are seated in selected rows for 'operational reasons'. Then in the next sentence, they said I can change by paying (my take: Children can only sit in certain rows because, well, 'operational', unless you pay us more, in which case, 'operational' concerns don't matter). To be clear, I apparently cannot change by paying either, since the website errs out.

Any thoughts on how to deal with this (preferable, without waiting multiple hours for AC to answer the phone), and if there is any actual restrictions where kids have to sit in the back.

Update: Twitter still insisting that ‘operations’ are why kids must be assigned in back, basically, because it screws up back to front boarding, then proceeding to send a link of zone boarding disproving point because it correctly shows business and credit card holding pax, both presumably not sitting in the back rows, boarding before families. Decided to call, waited 45 minutes (only because it was after midnight) for an agent to tell me it’s because I was assigned the seats for free (which also does not explain why it needs to be worst seats on the plane instead of the multiple rows ahead of this that are empty), then told me if I wanted to select before online checkin to select and pay for online - which again, I can’t because the website is erring out.