Reporting identity fraud

Hi,

I am not an ID mobile customer but have just received a letter regarding an account that has been set up in my name. I have recently been a victim of identity theft and have had lots of mobile phone contracts set up using my details with various providers. 
 

The live chat does not work on the IDMobile website and I cannot find an email to contact or a number to call where it is actually possible to speak to someone. 
 

How do I go about reporting this and get the account closed?

Thanks