Which bank in Nigeria has the best customer care service?

Customer Service rendered by organizations in Nigeria is improving by the day. Banks handle alot of customers and clients, so they are more open to criticism by these customers.
But i would add that for a country like Nigeria where it is hard to practice the Customer Service rule 'The Customer is always right', because customers tend to take advantage of this rule, our banks render satisfactory customer service.
But if you have a particular bank that you think is exceptional, or should improve, which would it be?