They had no right to leave anything in your home without your consent or permission: as soon as you closed, it was your home after all, not theirs. You have no obligation to let someone come by or into your home to view items or buy them from the seller, and can refuse entrance to anyone you wish since you never agreed to this. You don't have to let strangers into your home. You may also tell the sellers that unless they remove the items at their expense within a reasonable time, at a time of your choosing, you will deem their items abandoned and dispose of them as you wish--you have to give them a reasonable but short time to so (say 5 business days following delivery of the notice). And you can tell the sellers that you will hold them responsible for all costs you incur due to their leaving items behind (e.g. if you have to pay to store anything elsewhere, or to live in a hotel/motel) and will sue them if they do not voluntarily pay those costs.All notices to the seller should be send overnight mail or fed ex with tracking, so they get it quickly and you can prove delivery; also, email or text as well, if you can.