A subsidiary of BlueCross BlueShield of South Carolina is laying off about 700 workers after losing two major contracts. The subsidiary, Palmetto Government Benefits Administrators, learned several months ago it would lose almost half of its business this year. The Centers for Medicaid and Medicare Services issued a notice recently that a contract for operating the national (800) MEDICARE hot line will expire soon. About half the job losses will be customer service representatives from the call centers. The rest are claims processors, appeals processors and managers.