Cortel (aka BluePrint) has maintained our phone systems for over 10 years.
I only have positive things to say about this company and their staff. Their technical departement is unsurpassed in the industry.
We recently had our security system upgraded by Cortel (the original system was not installed by them), and the system is working flawlessly.
Their sales office is in mid-town mahattan, and I would recommend their services to medium-to-large businesses looking for a one-stop solution for voice/network, as well as security implementations. They have the ability and expertise to cover it all.