Hey Sonia,

 Did you happen to get the cel on ebay? If you 
won it as an auction, then there is clear 
evidence of the amount that you paid for the cel. 
Or, if you got it from a dealer, I would think 
that they could mail an invoice to you which 
would show the value of the cel. If it was a 
private sale, I'm not sure what you can do. But, 
I do believe that you can use auction info or 
dealer info to prove the value of the cel. ;) I 
hope this helps. Some post offices have different 
policies for some reason!

Take care,
Robin ;)