Indraprastha Gas Limited [IGL] — Bill on Connection which have been asked to be closed 3 years back

This is regarding BP # - [protected] mapped to D133 FF Saket. I had asked for the connection to be disconnected but it did not get closed and the buyers of the house used the connection and paid. I repeatedly over different whatsapp numbers have communicated that the connection be disconnected byt the amount of bill has now become Rs 10K+ whereas, i have sold off my house 3 years back.