Level 1 Maintenance Refuses to pay and has breeched the contract, not answering emails or taking calls Dedham, Massachusetts

I was contracted by Level 1 Maintenance to do snow removal for them back in December. I was given one time service tickets until they finally drew up the final contract. They gave me 5 stores to start then increased it to17 because I was doing a good job. They responded to every call and email when we started. They were so helpful that I emailed their boss and told him how great the staff was. (He never replied)

However, when it was time for them to pay the bill everything stopped. My account rep (that I spoke with several times per day) now only returns 1 out of my 10 emails and my calls go to voice mail. The A/P department only answers email every other week or so if that.

I told them that all I wanted was an update as to when I would be paid and that's all. Still just a run around. They told me that I wouldn't be paid for a couple sites that didn't have signatures, however 1 of the sites was a vacant lot that we provided pictures for and the other was a due to an employee refusing to sign and that one we were told by Level 1 staff to do the work and they would approve it. I even ad the call time and the name of the Level 1 employee that approved it. I emailed the boss again to ask for help and still (go figure) NO ANSWER!!!! 

Level 1 seems to pull this in every city with too many of their contractors. How do they stay in business??? 

I'm now over 75 days on my first invoice that I was told net 45. My next step is to place liens on all of the properties to get my money. 

If you do business with them - good luck. I have yet to find ANYONE that has been paid as agreed upon.