I bought a house in PA that has a propane tank on the premises that is rented from a propane company. I got quotes from this propane company and decided not to go with them. I received a contract with the quotes and did not sign it. They tried to charge my credit card, but I called them and they removed the charge as I made it clear I was not using their services. They now want to charge me to remove the propane tank and state they will send me to collections if I do not pay the charge. Can they do that? They own the tank, and the previous owner rented it. I never have conducted any business with them.
In most contracts, the parties sign in their capacity as people (or agents for other people). However, some contracts are signed in the capacity as the owner of a piece of land and the contract transfers with the land. The liability rests with the current owner and, if unpaid, creates a lien over the property.
These are particularly common in contracts with utilities or where the contract involves the a structure on the land. Surprise, surprise, the situation you describe involves both.
You need to refer back to your contract for the land as these types of contracts are usually disclosed (unless they are a function of local law because everyone just knows - I don't know anything about Pa. law on this) and the original contract with the gas company. Your settlement may have also involved you paying a figure to purchase the gas in the tank as at the date of settlement.
For example, in new-south-wales, council rates and water rates attach to the land as a matter of law and the vendor pays the purchaser for any amount they have paid in advance (or vice-versa if they are in arrears). Electricity and piped gas don't; the vendor ends their account on or before settlement and the buyer opens a new account on or after settlement and each pays for their own use. Propane for portable bottles doesn't but for fixed installations does as a matter of contract with the gas company.