We've been with Post Office Home Insurance for about 2 years. Over this time we had renewed our policy even though the premium had increased to over 40% without making any claims. (We were busy at the time of renewal!).
Unknown to us, and at a time when we were away, they tried to automatically renew the policy for another year but failed because the card I paid them with previously, had expired. Continuous Payment Authority (CPA), which they impose upon you when we took the policy out.
Due to the unexplained premium rise, we did not intend to renew at the end of the policy, and unaware of the CPA at the time, the Post Office were still expecting payment for another year.
Within a month we found that they had imposed a cancellation fee of £44.23, removed all policy documentation from their "self-service" portal and were expecting us to pay it without providing us any documentation or explanation.
Given no choice by the debt collection agency and not wanting things to escalate, I paid the debt.
Point to note: many companies bind you in with CPA, FCA should take note and make it mandatory for insurance companies to offer customers an "opt out" for automatic renewals.
Thats one way to stop customers getting fleeced with unreasonable premium rises.