I find the GS email pretty useless as they can never help you with anything in the future. Not even change a seat.

On 3 occasions I’ve now used the facebook messenger app to contact United and have received amazing, quick and efficient assistance on questions about active booking.
Like change a complex saver award, fix a crazy situation when P fare changed to G fare between purchasing and ticket issuing, fix some upgrade issues due to rebooking.

So I would gladly recommend for excellent assitance !!