Waste Management [WM] review: Terminating account after selling home

WM has done a great job with its service up until I called on February 3 to say we sold our home and needed to terminate our account. After speaking to a couple of representatives finally ended up with Jose Saldivar who said it would be no problem ([protected]@wm.com). He sent an affidavit to be filled out. I had our Realtor fill it out and then he said I needed to fill it out. I did that and he responded that the contract had been cancelled but a fee needed to be paid to remove the dumpster. I asked for him to invoice me and he has since not responded to any of my emails. In the meantime I'm getting invoiced for another month and we no longer own the property. Can you help?