Omni care OMNI CARE GOT US TOO!!! Long Island New York

So they Called us for emergency service in November for Pet supplies Plus telling us they have NO heat and the animals are going to die. They told me the payment terms were 30days so I dispatched my guy we then received 6 more calls for Pet supplies all over Long Island. When 30 days round around and we still didn’t received a payment from them we stopped all work but they already racked up a $3000.00 bill for all the stores. I called and called got the run around. So then I called pet supplies plus direct they told me they already paid omin care for the work we did and cannot pay us again! SO I am filing a mechanic lien against the building. Complete Bull how do they get away with this?????