Post paid to prepaid connection

I have applied to change my sim card prepaid to postpaid but the reliance outlet of kajipara saying that system not taking my request i called to customer they are telling that it is the reliance outlets duty where i submitted my document. Please help me to change my sim card i am very old customer of reliance and the number i am using that one also very old. I am also using reliance landline connection. i am really surprised how reliance communication can do such thing with there old customer like me.

My Relienace mobile number is +919331726416
My alternate number is 9748175962 if my problem is noticed and any step taken please notify my in this number
9748175962