Apologies if this sort of thing has been answered ad infinitum but it wasn't obvious in my searches.

I have a booking for myself and two children. After the booking was made it turned out my partner could come so made their own booking on the same flights.

I asked the chat bot to add my partners booking to mine and the response was along the lines of "the more the merrier just call the 0800 number".

However when I called the agent said this was not possible which I found surprising (maybe so people can't book as smaller groups to avoid all being in a higher priced fare bucket?)

Is this standard procedure and nothing we can do besides seat selecting together? Are there times when the agent would be more amenable/helpful?

Thanks