Vodafone — Postpaid to prepaid connection conversion issue

I had submitted a prepaid to postpaid connection application on 11th july 2020 in Vodafone Store, linton Street, Kolkata. Upon submitting the request I was given a prepaid sim and was told the connection will be active in 2hours time. But till today the 18th july my sim is not active as it is showing sim provisioning failed. I have visited the Vodafone store Linton Street many tomes but my problem has not resolved. The service personell at the store are assuring it will happen in a day's time.However a week has passed and my problem still persists. I am very offended with the quality of service.