Service bond

I worked in BSNL as JAO for 1 year only. I leaved BSNL and joined UPPCL with prpoer permission and NOC from BSNL. I had served a bond with BSNL to serve atleast for 5 years but I complete only 1 year in that organization. Now, at the leaving of BSNL i also served the BSNL a new bond that I will serve UPPCL atleast for Balance bond period, But after joining UPPCL, BSNL served a notice to surety and me to pay the bond money because there is no any condition of bond in UPPCL. I answered that that's why I give undertaking to BSNL for a fresh bond in the light of DPE 2004 Guidelines. But now they are forcing us to pay. What should I do?