Idea Post paid Connection
Deactivating the connection

I had an idea postpaid corporate connection. when i left that organization i have given a letter to Idea office at Adoor. It was on july. But still phone bill is coming to my previous organization addressed to me. Its adding the previous bill till date. What should i do? I have given written letter for deactivation and when we enquired at that office they said they have submitted it. So what should i do?