We were listed as the HVAC subcontractor on a school project. During the initial construction phase we requested further clarification on the project due to poor plans so we knew where to start. At that point it was discovered that the school was providing the HVAC portion of the project with the mobile classroom purchase. We were then issued a change order deducting the job total and canceling our contract. Now a year later the GC is coming back asking us to sign an unconditional release. We were never paid nor performed any onsite work. Should we sign the unconditional or do something else?