Mtn insurance

I changed a contract to prepaid last year July.This was done but never was it mentioned that there is insurance, .I never received statements,was just handed over for collection.Only on enquiring I was informed of the arrears amount.I was informed that the insurance was taken out when I upgraded in Oct 2019,which never happened.I asked for the proof but up to date never received anything.I did pay the outstanding amount but are still receiving calls?