Before Elon Musk bought Twitter last month, the company's executives had racked up hundreds of thousands of dollars in travel invoices that the social media service planned to pay. But once Musk took over the company, he refused to reimburse travel vendors for those bills, current and former Twitter employees said. Musk's staff said the services were authorized by the company's former management and not by him. His staff has since avoided the calls of the travel vendors, the people said. Musk has embarked on an enormous cost-cutting campaign since closing his $44 billion acquisition of Twitter. He initially slashed half of the company's 7,500-person workforce, fired workers and continued with layoffs as recently as Monday.