l had a local mechanic replace the rear brake pads and the wire sensor. The light is still on.

so is mine!

have you checked the brake fluid level? and front brakes?

Turn the key on without starting the engine. The brake pad light will turn off by itself in approximately 30 seconds.
Are u sure u have the model/year right?
EDIT:
Perhaps u also need to check the condition of the front pads & sensor. Or the rear sensor is not properly inserted to its connector.
The year & the model is important in newer BMW's. Most newer models' brake pad lights can not be reset in the usual way, & instead requires resetting through the instrument cluster controls, or with the use of a GT1.

BMW or MBz? Model E320 or 328? It does not matter, the answer is the same. Front and Rear brake pads have only one wheel with a pad thickness sensor. The sensor may not be connected or the front pads may be worn down.