Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Communication Breakdown; Confusion
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Environment - Non Weather Related; Human Factors; Procedure
On the GRNCH arrival. Landing south. At approx. BUGGZ int; airport changed to landing north. ATC tells us to expect 36L. We change the arrival to landing north. Shortly after; ATC clears us from 11;000 ft to 7;000 ft. We readback. Passing 8;000 ft; ATC asks us; says did he give us 9;000 ft?  We say no; 7;000 ft. He tells us to maintain 8;000 ft; we climb from 7;800 back to 8;000 after advising him we were passing thru 8;000. ATC was busy to begin with and they got busier with the runway change landing south to landing north. At times; the controller sounded confused regarding our clearance; at one time asking us what fix we were flying to. I know that new arrivals have started in many cities; and do not know if this was a factor. It was the first day of the new database.We did nothing wrong. Proper read backs were given. We were busy from south flow changing to 36L then to 36R while working around some weather and managing the arrival. The controllers were very busy. I am concerned about the altitude assignment and the controller changing the altitude assignment. We have confidence that we received a clearance to 7;000 ft.We worked hard to communicate with the busy controller and use proper radio phraseology. We were very surprised when he asked about our altitude as we were sure we were where we were supposed to be.
Pilot reported possibly over shooting an assigned altitude after being questioned by the Air Traffic Controller.