capital one financial cof fell 35 in premarket trades monday after reports that walmart inc wmt sued the creditcard giant in an effort to scrap a creditcard partnership the wall street journal reported that walmart has filed its suit because capital one allegedly came up short on its service obligations such as failing to replace lost cards or post some transactions to customers accounts in a timely manner capitol one said the claims were immaterial the journal said capital one plans to vigorously protect our contractual rights in court a spokesperson told the newspaper