Message under telephone number

Hi

I have inherited a website using the ample theme https://www.ukdetectives.uk/. I need to put a message under the telephone numbers in the header to say “all calls to the 0800 085 6853 are free from landlines and mobiles” I can’t work out where to do this.

I would really appreciate any help or suggestions.

Thank you

The page I need help with: [log in to see the link]