Carvana Co. canceled a $1 billion debt swap after a group of creditors refused to exchange their notes, posing a challenge as the used car retailer attempts to rein in its debt load, Bloomberg News reported. The online automobile seller failed to convince holders of at least $500 million of notes to participate in the exchange offer before the deal expired, according to a statement Friday. The swap’s cancellation marks the latest blow for the Tempe, Arizona-based company, which had sweetened the deal terms and repeatedly extended the timeline in a bid to lure investor participation. A group of debt holders, including Apollo Global Management Inc. and Pacific Investment Management Co., came together last year in an effort to negotiate with Carvana in preparation for a restructuring. The cohort opposed the debt exchange when Carvana first launched it in March, with some lenders proposing alternative deals.