Customer service definitely not lofty

We had work done by this company several years ago, and were happy with their work. When we decided to use them again to install a small storage loft in our home, we were expecting good service. This proved not to be the case. They did not properly convert the whole area they said they would, and when I raised this with them, they argued that that was the plan all along. I was told we'd get a 3m by 4m storage loft and expected an open floor area of more or less that size, not 3/4 of the area properly opened up and the last 1/4 with all the roofing timbers still in place (2 trusses unconverted). I also noticed that they had removed the supporting timbers from one other truss without properly reinforcing it as they had the others. We had to pay extra to get the 2 trusses done (which should have been part of what was quoted for the original job), and as they did not have enough materials, I had to supply materials on the day for them to reinforce the truss that was not properly reinforced with the original installation. They did not have a particularly customer-focused attitude when I expressed my dissatisfaction with the first installation and with the "corrective measures" they took - I got the impression that the predominant credo is "the customer is always wrong". In the service industry the saying is that you are only ever as good as your last job, which is why we certainly won't use this company again.