Circle Chevy, Shrewsbury, NJ review: Overcharging for service

I own a 2019 Colorado 6 (cylinder, VIN # 1GCGTCEN2K1350450) with 35,000 miles. Recently, I noticed my right front headlamp was out. I replaced it with the same type bulb. However it still did not work. I brought it to Cricle Chevy Service in Shrewsbury, NJ (thinking I can trust this dealer) at 7 am for service. The first agent told me there was a $200 diagnostic fee alone that can not be used toward the repair. I questioned him anout this charge. He said it is standard cost. Three hours later the agent called me and said my truck was ready. The repair was a broken harness to the light and to replace the bulb. The total came to $470.52. I questioned the service manager about the cost. He told me this is standard costs. I am retired and on a fixed income. I think these charges to repair a simple harness and bulb is unfair.