How do I get a proof of useage for my phone (for an insurance claim)?

I need to obtain proof of usage for my insurance as it’s still showing the number that came with the phone which I switched to my normal number. How can I do that please?

Thank you 

Hi there, I sorted this by emailing documents@idmobile.co.uk and asked them for proof of usage (for insurance policy to change my number over) and had to provide my full name, address, date of birth, phone number. They sent proof of usage by email to me the next day.
The phone number on my insurance was the one they sent with a new phone which I switched back to my existing number so needed to change it in their records in case of a claim. 
Hope this helps other people get sorted too.

Thanks