Reliance Jio Infocomm — taken connection as prepaid but now i'm getting billed as postpaid

Address:	YSR, Andhra Pradesh, 516001
Website:	jio

I have taken prepaid no [protected] but it now iam getting the bill as postpaid how it became as postpaid with out my request from last 2 months iam paying the bill but when i have taken the connection i have not been charged for postpaid but now iam getting charged i want my post paid connection to prepaid connection and i don't want to pay any charges and i want the paid amount also to be returned