make "contact me" simpler

Dear WordPress,

I am not good with computers.
I’m not good with WordPress.

In light of that I helped a friend with two websites,
– answers
– nyn

The problem is, the phone number, sometimes changes.
But, I placed some contact information on each and every page.
So, when I have to change the number, I have to do it on every page.

Can someone suggest a better option?

Thank you.