Adjust premiums to current value

Just had a claim with Standard Bank for my cellphone. When I bought the phone 3 years ago it costs X-amount and was insured for X-amount. But now the value has dropped to Y amount which I understand but my issue then why doesn't the premium go down as expected, aligning to the current Y amount. I need to also align the cellphones that I currently have insured. I left a "call back" from the APP but no call back yet.