Maybe try burning the service manager by telling BMW NA the dealership is flatly unresponsive. You will get a response. You gave them a chance.
To see if they replaced it for real you might check your paperwork of the service visit. My replacement speaker on the paperwork was noted as:
- 0058500 Verifying Customer Concern and Diagnosing Cause
- 4617 WB (N/C)
- 1 65-13-2-622-468 Top-HIFI Mid-Range Loudspeak : 651031 (N/C)
- 6513560 Removing and installing/replacing the loudspeaker
- 4617 WB (N/C)
- FC: 6512001200