Reservation sys files

Hi Computer system Experts!

I need your help re: Sheraton Dallas Hotel Online Reservation.

I made a reservation then cancelled it online, but Sheraton Dallas Hotel charged my MC for one night for "No show ".

Because they did not send me e-mail confirmation for both reservation
and cancellation, I have no way to prove my cancelation.

In e-mail they said:
“At the time you booked your reservation online you did not have your email address noted.”
 
I have been traveling for the past 10 years and  reserved Hotels online, and  I never forgot to give my e-mail address
not even once, so how could they say that I forgot this time ?
I  believe in keeping expenses low, if I don't give my e-mail address, I may end up paying expensive long distance call
to communicate, as many hotels have no toll free numbers for dispute solving, so it’s impossible that I forgot to give
my e-mail address! Unless someone manually erased my e-mail address for unknown reason.
This I see as indication that a computer system error existed at that time

What do you advice me to do to solve this problem ?
Maybe computer system record ? In that case what particular system file I should ask them to mailled to me.
Is there any way I can spot if there was any tampering? Like erased my e-mail entry, erased cancelation request?
 

 

As a long-time traveler, my advice is to do all business over the phone and keep handwritten notes, including confirmation numbers. It is easier to carry a cell-phone and a a little notepad. I mean a notepad made of paper, no a computer. 

If you are a business person, your greatest assert is your telephone manner and presence. Talk to people, but be polite, let them remember you. And trying to save a dollar on an important phone call is not a good business practice.