On May 8 2002 I wrote the following email to
customer.services@vodafone-retail.co.uk:

I contacted you earlier concerning the double charging that had occurred since you moved me into a multi-sim agreement without my permission. At that time the bill was not intelligible even to the staff of my local store so it has taken a few bills subsequently to understand what is happening.

I now see that I am being credited for the advance payments I made for line rental but that the multi-sim rental is still in place. I would like you to remove the multi-sim rental because:
I do not want it
I did not ask for it
It was provided without my express permission or warning about costs & T&Cs;
I was not told it would cost anything
I was not told it would last 12 months
I do not use it (my other phone has been broken for some time)
Most Vodafone staff do not understand it
It has caused loss of service for several days each time I replace my phone
I cannot find any mention of this service in your published tariffs
The cost is obscure in the itemised billing
One other bizarre consequence of this sad tale is that international barring has been introduced on my line, again without my request or permission. Please restore this and remove the multi-sim.

Since then I have had no reply even though I have written a couple of times since to ask if they answer their mail. I have noticed that they are quite fast to respond to sales enquiries but are rather reluctant to answer anything that appears to be a complaint.