West Corp. plans to close its call center in Hampton by March 31, putting 450 people out of work. The Omaha-based company announced the closing yesterday, citing a drop in business by companies that use the center to handle customer calls as the reason behind the closure. Some of the workers will be invited to apply for positions at the company’s 47 other call centers. The Hampton operation opened in 1996. City officials are offering to help displaced workers find new jobs in the communications industry or to assist them in job training for new employment.