Aviva insurance 'conveniently' lost my call recording when I was disputing my car insurance around 7 years ago. Didn't add a second driver, got my address wrong & didn't take account of any NCD.
Wanted to charge me £35 admin for each amendment, despite me giving them the correct info over the phone. As it was within 14 days, I said I wanted to cancel the policy & followed up with a letter confirming this. Apparently the recording of both calls was corrupted by a power outage & my letter arrived on day 15, so they wouldn't cancel without a further charge (think it was around £70, more than 3/4 the cost of the policy). Went through the Ombudsman who also couldn't access the recordings, but as a 'good will gesture' Aviva agreed to make the changes to my policy free of charge.
Still shafted me though as when I eventually changed insurance the following year my 10 year NCD changed to 5 as they said that was the maximum they did (small print).
Depends on who you deal with as to whether the recorded calls are useful or not. In my personal experience (and I've been a call centre trainer in the past), it's not done me any favours.