Anyone at the workplace can revoke permission for the collector to call you there. You can limit or halt all calls to any place in writing, assuming your pursuer is domestic. Using a job as ''collateral'' is just the sort of ignorant remark I might expect from a fake payday loan collector in South Asia.
Learn how to exercise your FDCPA rights as an alleged debtor at FTC-dot-gov. See also if your state laws are stronger.