You pay someone to build you a house to a certain budget and within a certain time frame – and they do this. Is this good or great service?
Some clients would think so. It is actually disappointing that some clients think someone doing what they agreed to do and you paid them to do is good or great service. This is just the definition of service.
You need to redefine the expectation of the client and yours. This isn’t about under-promising and over delivering – it is about proper client centric, solutions driven service aimed at helping your customer (not just you).
Sure, you need to do the piece of work the client engaged you for well – but memorable service comes from the extra service you deliver that the client didn’t expect you to deliver but is meaningul to them.
Also refer Win, Win, What?