Welcome!
You have two problems, and they are not related to each other.
1) The mirrors are definitely controlled by the driver's door module (DDM) that also controls the power window and locks. Do you have any problems with window or lock control? If not, you might just have a failure of the mirror control switch or the wiring from the switch to the DDM. Are you good with electrical troubleshooting, or do you have an automotive electrical technician to get help from? The dealer could also troubleshoot it, but for a price that is probably higher.
2) The seat belt chime (bell) is controlled by switches that are wired to the BCM (body control module), but the final thing that makes the noise is the radio, using the left front speaker. Did you just buy this vehicle? Did the chime used to work, and is now dead? Or was the chime always dead? If you have an aftermarket (not original equipment) radio, the problem could be that the person who installed the new radio did not use an "adapter" that is required to keep the chime working. Please tell us about the history of the vehicle.
Thanks.