Idea Cellular — Unable to migrate from postpaid to prepaid

Address:

Junagadh, Gujarat, 362001

Since 2008, we are using three Idea postpaid connections.
Many times I have found the billed amount is accessed than our use which is due to extra addition of sms and std charges.
Four to five times, we went and told them to migrate to prepaid as we dont want postpaid service any more but, every time, they explained and convienced my father with their marketing skills.
Even I had to travelled all the way from Gandhinagar, Ahmedabad, Rajkot and Porbandar but, no use.
Our billing date is 8th of every month.
So yesterday we went there, paid the bill and requested to migrate to prepaid and they said internet is not working. Come tomorrow.
Today my father again went. They talked with him and again said please tell your son to come to the office and we will explain the plans.
(In past, I went their alone and they said, please bring your father we will explain the plans to him)