Bad workmanship

We had a leak in one of our flats. They gave a quote and my boss said they can go ahead. After 2 days it started leaking again. I phoned them again to fix their sloppy work, but every time they promise to go out. I made a few appointments with the tenants, but with no success. I have send out another plumber today as the water was poring through the ceiling. On his review of the work, NTBD did not do anything, they just patch the one pipe. Please do not us them at all. They are terrible and unreliable. They do not reply to any calls or messages.