I have yet to have a chat agent actually accomplish what I needed/wanted. The worst are when they either ghost me after I've invested about 30-40 minutes or screw something up so badly I have to either call res and get a supervisor involved (downgrading me from PremPlus to Economy on a segment they shouldn't have even touched) or make an extra trip to visit the airport to have an agent fix it.
My result is that I don't trust them and I find the process to take more effort and be more cumbersome than just calling (or indeed talking to an airport agent when within 24 hours of travel)