I had a small restaurant, and on 2006 i subleased these business?

my leasing ended on march/2008 i never had any problem with the people who was running the restaurant but, they decided to do the same thing after 6 months and they sold the business on feb/2007, they ask me if they would do this and I say ok but they should still paying me the rent cause I had the commitment with the landlord and I was responsible to pay the rents so they always paid me until my leasing finished, But my guarantee was the restaurant equipment. The "new owners went into a new leasing for 5 years and it supposed they should pay me the property taxes for the furniture and equipment of 2008. But when I was paying my property taxes online I decided to check if this account correspondent to the business still under my name, unfortunateley it is and not only that, these people never paid the taxes so I did it and now they don't want to pay me that money. What can I do if I never signed anything with them. The people who did the agreement were my buyers and now they are trying to collect this money for me but he second tenants just moved out from hte space in the middle of the night and they took out all the furniture and equipment. I have found them but it supposed that my buyers must go and ask them to pay me the money since they were the ones who sold the business and they signed the contract with this people.

What can I do?

Thank you for any help