If it sounds like metal on metal - more crunchy than screechy - then the brakes need to be replaced.
If it is a screeching sound that seems to have popped up randomly, it could be contamination. Try bedding in the brakes
Bedding in bike brakes involves transferring a thin, even layer of brake pad material onto the rotor through repeated, controlled stops to maximize stopping power, eliminate noise, and prevent glazing. On a safe, flat area, accelerate to ~15-20 mph and apply both brakes firmly to reduce speed to a walking pace without stopping completely. Repeat this 5-10 times.
If it does not resolve the issue, contact your shop's service team.