Changed my surname now want me to do an affidavit

I am really tired of having to complain about metropolitan and if I have not had my policies for over 7 years I would cancel. Their service is pathetic, In June last year I forwarded my marriage certificate for their records given that I had a spousal cover/benefit in my policy. I stated clearly in the email that it was for their records and my surname remained unchanged and if it change I would forward d new ID copy. In dec-Jan I realised that they have changed my surname. I then sent email querying this and no response was received, I then called 30 Jan 2015, and was told the email box was full so some msgs were not going through. I requested change back to my surname stating I have not changed it to that of my husband's. I thought this would be sorted as I resent previous emails but now got an sms saying I shud get an affidavit saying I am using my ****en surname, question is did they get any new ID copy reflecting new surname? Why then did they change my personal information without my authorisation. Legally I am not compelled to change my surname once married, also I forwarded my husband's ID copy in 2013 so he could be added to my spousal benefit yet this has not happened!!!!