It's on the form
Directly from Form 4, instructions 8:
Any inquiry relating to the status of an application to transfer an NFA firearm or about procedures in general should be directed to the NFA Branch at (304) 616-4500.
NRA Instructor: Pistol, Home Safety, Personal Protection, RSO, Reloading.
NRA Life Member, NRA-ILA Sustaining Member, AZ CCW training org. & instructor, AZ HE instructor.
JWsGUNs.com FFL-07, NFA SOT-C2.