bought house in 2007 that has propane tank for garage heater. 2015 a company says it's leased @ wants it back

8 years is a long time to have a leased tank and not make a payment.  Don't know if this is truely leased or not.  If it is give it back.  Make the leasing company prove it is thiers.   The tank is likely personal property not included in the purchase of the home.