Can Insurance Rescind Their Offer Under Insurance Law?

I have an extended warranty with domestic and general for my tv. I was told it was uneconomical to replace, so they offered me a new tv. I was happy and excepted the offer, as it was actually an upgrade. They advised they had all the paperwork processed and the tv would be shipped from Sony in New Zealand as I am in New Zealand.

They had mucked me around for 9 days by this stage. They said they would call me the next morning with the delivery day and time. They contacted me the next day and had changed their minds and were now going to fix my old tv. Lucky for them, when I was making the call to arrange the delivery of my new TV, Sony in NZ said they will replace the LCD panel in my tv for free at no charge to the insurance company.

Can an insurance company verbally make an offer and then rescind that same offer under Insurance Law? I thought if it was verbally agreed to, it was considered a verbal contract/agreement.