Check to see if your contractor has a North Carolina license. See link below.

Understand that a person or company do not need a license to service units in NC. The must have the proper license to install or replace a furnace or air conditioning unit. If any service technician is handling refrigerant. That tech must be EPA certified and should be carring his or her certification card with them.

https://onlineweb.nclicensing.org/Lookup/LicenseLookup.aspx