Final answer:
The Defense Finance and Accounting Services (DFAS) should be contacted to rectify a DEERS discrepancy for a retired service member.
Step-by-step explanation:
To rectify a DEERS discrepancy for a retired service member, the person to be contacted is the Defense Finance and Accounting Services (DFAS). DFAS is responsible for managing military pay and pensions, including DEERS (Defense Enrollment Eligibility Reporting System) information. They have a dedicated customer service line for retired service members and their families, where they can assist with resolving any discrepancies or issues related to DEERS.