It can be well worth keeping a log of phone calls to companies such as banks, utility companies and anyone else who you have an account with. You never know when it could be useful to have this information.
For example this week I received some unsolicited credit card cheques from Natwest. I have previously been sent these by Natwest and I remember that I phoned them up to ask them not to send them to me anymore. I know I have called them at least once and I suspect that I have called them twice. As they are clearly not honouring my preferences I am writing a letter of complaint to them.
Unfortunately I don’t know the dates (or even whether I made one or two) of my calls to them. I can still write the letter, but if I had recorded my calls to them I could have been very specific about details of when I told them not to send me any more of their credit card cheques.
Here is the call logging XLS spreadsheet that I’ve put together to record future calls.