Great Lakes Roofing

I bought a commercial building they had replaced the flat roof on in Neenah, Wi. This was part of the agreement to purchase the property. Great Lake roofing from Neenah/Menasha did the work. This is a spancrete roof. The spancrete has a few cracks Great Lakes roofing ran the membrane down 1-2 inches so the first time it rained the roof leaked. Either by the cracks in the roof or the seam where the roof and wall meet. I called the "salesman" and asked him what to do... He had to ask his "manager" and get back to me. He called me back to let me know it would be an extra $1,500.00. Mind you the original project was less than $5,000.00. I said I would be willing to pay something so we can get this resolved but over 20% for the roof still leaking. That is crazy!! I texted pictures with this note attached. "This is pictures of the roof that is leaking. As you can see the concrete is over 8" thick. And is cracked and leaking. Please let me know your plan of action. " within an hour the "district manager" called me back screaming at me to leave his salesman alone. And he told me his name and spelled it for me. At that point I told him my next action would be small claims court. His response " I will counter sue for wasting my time" I hope someone higher up in the company would contact me and we can get this resolved.  Thanks.