I told the Post Office to ship the package by 
airmail but it still took a month to get there.
Don't know why?  

Was very worried as it was an expensive cel. 

It was insured and the Post Office told me that I 
had to wait 31 days to make a claim because it 
sometimes took a long time for mail to arrive.  
Sure enough almost 31 days latter it showed up to 
the buyers address.  

So maybe have the buyer wait at least a month 
from the time you shipped the package before 
doing anything.