Vodafone — UPC Can not generated when I try to port [protected]

Dear sir
I used Vi prepaid sim card No. [protected], from few months I try to port another network. I send SMS PORT [protected] at 1900 sms delivered.
I can not received UPC code.
I received reply from 1901 That UPC cannot generated for the reasons (1) There are subsisting contractual obligations with your service provider. Please contact your service provider for further assistance.

I contact service provider more times. but there is no result. I visit Vi store but my problem is not resolved.
Kindly resolve problem as early as possible.
This is second time I registered complain. I call customer care more time. but problem is as it is.