Remote pings and MailChimp setup

Hi,

http://us7.api.mailchimp.com/1.3/?method=listSubscribe

apikey=abcd123-us7
id=123123123123
update_existing=true
send_welcome=true
email_address=%useremail%
double_optin=true

Hi, these are my remote ping settings. It doesn't seem to work with the standard subscription signup as it doesn't ask for a First or Surname and MailChimp seems to want this as this comes up as the response of the API request in MailChimp "(250) List_MergeFieldRequired - FNAME must be provided - please enter a value".

I have had this problem with the MailChimp plugin you have as well. How can I get this to be integrated with Membership if the subscription form doesn't ask for FNAME and SNAME?

Thanks,
Louise

P.S. I have screen prints of my settings if you want them.