I would just say, If u sue company it is very long procedure for MNP instaed u try again.. are you an Heavy user ?
I remember it happened to many I Know. They were Idea,Bsnl customer from very long Years and they wanted to shift to airtel. their request was Rejected first time. when I asked for the Reason. Officers/employees said they just want to make this process difficult so customer stop this process. Only to those customers who were long with them and/or who had very High Billing.
But when they applied again, It was resolved almost. (It is just company took little long time to transfer then usual ). they did it partial by just having incoming calls and day later starting outgoing.. But finally it was done.
so better try this, then that u wish too.