About Propane Tanks and Taking them with me in bad Health?

My mom and then me have been renting 3 now 2 gas tanks from the same company they downsized my sons tank a few years ago saying we werent buying enough propane. I just got a letter and we have 66 percent gas in our tank and my son doesnt have any its summer not needed they sent me a letter saying i can either buy the tanks or they are picking them up that leaves my son no heat no cooking and me i am in bad health with 2 open heart surgeries an i have diabetes and vascultis and also neuropathy and they take my gas tank i have no way to cook or eat or nothing. I am not behind on rent or anything I have receipts for almost 1000 dollars i spent on propane they are saying i only bought 175 gallons which is a lie. Can they legally take my tanks and leave me with no way to cook or eat