It's cheaper but ineffective. The trick is to use automation as much as possible and not a drop more. Excellent customer service agents are actually helpful for this. The agents you have aren't mindless drones, they're people and they don't want to do yet another stupid call where they explain that button X does thing Y, even though it's labelled X, they can gladly explain what needs improving because they're interacting with your customers all day - and then you can fix it. Cherish these people.

My good bank (First Direct) has done really well at this. I can call them about anything 24/7, a human answers about as quickly as a person would answer their own phone, maybe 5-10 seconds, not long enough for one of those stupid "We're very busy" messages. But I rarely talk to them because all routine stuff just works correctly so I don't need to. I called them once to ask what happens if I need a whole lot of cash right soon (since they don't have physical locations, the answer was for very large amounts I need to give a lot of notice but a courier brings me the cash) and decades ago I called them because I wanted my debit card to work in the ATMs for other banks (remember when it didn't? Maybe you're too young). Also I called them to transfer money to buy my current home because that's too much money to be authorised by a web form apparently.