Give me the value of a phone I insured not lower value

Policy number *** I insured my cellphone iPhone 11 128g and it's now ******! I claimed from them they told me I must produce proof of purchase! I called istore who provided me with a receipt which I forwarded to Sade Dixon, she called me yesterday and said they will replace the phone but give me a 64g ! I told her I've insured a 128g so they can't give me a 64g, ( unless if they want me to go back to istore to tell them that auto and general says that the proof of payment you gave me is the the truth of what I bought) secondly they do not want to give me a choice to select a phone if my choice because il top up the price to get a new phone! The other thing is why when you insure your phone don't they want a proof of purchase! But they want it when you claim ? This is not fair !