Well Said Alex,
If you remember, this is how the serivce industry works (My previous company Clasticon Solutions), and Probably the good reason Why the customer chooses to speak to you the next time he call up the office, He will not be ready to talk to any one, even your boss, because you made it happen.
A contact of mine at Attest is still in touch with me even if I left the orgainisation, well He has also choosen to leave his company, but still he is in touch.
A well bonded relationship works when you speak for your customer at your workplace/ or to your team members and get what he wanted, sometime it could be free or if it is lot of work you charge him. As far as the service Industry is concerned "Customer is the King"