In a surprising "coincidence," a week to the day after an unsatisfactory phone call with A Plus, I got an email indicating that they "noticed that you do not have an account manager" and were assigning me one. Before I even read the email, I got a call from the person who had been assigned, indicating she was my new account manager and casually asking how things were going.
I knew exactly why they were calling and repeated my previous complaints, as well as indicated my plan to leave their services. After listening, my "account manager" apologized profusely for the unprofessional behavior of the previous person I had talked to, and offered to give me the domain service that had prompted my original call for free.
For the price of a phone call, an apology, and a $6 perk (well, it saved me $6; it cost them nothing), they kept a customer who pays them $50-$60 per year. That's doing business the right way.