Policy change mismatch

I took out a contract with MTN in 2015. At the time of taking out the contract, I ensured that I have insurance on the device before I walked out of the shop. At the time, the insurance policy I signed stated the different premiums to be paid and what the insured value of the deice is based on the premium. I had just gotten the Samsung Galaxy S7 Edge and as such took the highest insured amount available of R15 000.

It was a good thing because a few days later, the device got ******. I put in a claim and once finalized (within 2 weeks, to be fair), I was issued with a letter that stated that I can go get a phone from any MTN store up to the value of R15 000. At the time, the device was worth R15 600 but because my policy stated that I was insured up to the value of, I took the knock and paid the difference.

Fast-forward to July 2018 and my phone was ****** again. After the finalization of my claim, I was told the device would be delivered to a location of my choice. This confused me as there had been no discussion of what device I wanted (based on my previous experience, I could get a any device up to the value of R15 000). It was then that Pinnacle Marketing (administrators for MTN Insurance) informed me that MTN had changed their policy and sent a link to a document (where you have to click on 2/3 more links before you get to said document) to customers.

The new policy poses a significant change to the insurance type, stating that they will replace the exact model insured (which is now worth R3 500) unless said model is no longer available in the market versus what I understood to be in my policy of having the device insured up to the value of R15 000.

My issues 1. because an insurance policy is a legal document, is it allowed for the insurer to change the policy without getting acknowledgement of receipt and consent of the change from the client? 2. The document that I used to apply for insurance is still available on the MTN website today and states that insurance is for the value of the device at the time of indemnification yet the new policy does not reflect this 3. Not only was my premium not adjusted down to reflect the change in the value of the device but after issuing me with the replacement device, I recieved an SMS saying that my policy was updated to reflect the new device with "the sum insured value band of (R7 501-R15 000) at a monthly premium of R141.23" despite them having issued me a phone that is currently only worth R3 500 under their new policy.

Can someone please balance me because MTN seems to be contradicting themselves (policy change doesn't match up with premiums and isn't reflected in the application form) and I don't understand how a legally binding document can be seen as accepted without actual proof of consent.

I have tried to escalate this with MTN and Pinnacle Marketing and was told that I should go to the regulator with my complaint.