MTN not living up to their word

I took up a contract with MTN in 2016 at clearwater Mall. I was then convinced by the consultant to take up an insurance for the device and he made me get a cover that was over the value amount of the actual device telling me that" if anything was to happen to the device i would be covered for that value i was insured for". In 08/02/2018 I unfortunately lost my phone and submitted the claim soon after that. The claim was approved but my problem is that the insurance company wants to offer me the exact device i was using which has now 1. depreciated 2. The retail price of this device is way under valued to what I was insured for and told that if anything was to happen i would be insured for that value, further to this i do have the contact I signed when taking up the contract which stipulates the amount i'm covered for. when challenging this decision i'm told that according to their policy they cannot give me a device of that value and this is a policy i was never told anything about and I never signed for that policy .