When our case went through investigation we gave details of the call i.e the name of the guy we spoke to and the date and it could not be found. we also sent a fax saying "as per telephone conversation with ***** we would like to switch to SVR with no penalty. It seems everyone has the same thing written cause I remember asking him what we had to do and he said send in a fax / letter but had to be done within the next few days of the call.