If you are sending a fax from Japan to The USA or Canada using KDDI dial 001 010 the country code 1 for the USA and Canada and then the fax number without the first zero of the area code.
For the UK dial 001 010 the country code 44 for the UK and then the fax number without the first zero of the area code.
If you are using Softbank dial 0041 instead of 001. The numbers are the same for international calls from both landlines and mobiles.
Like this blog? Sign up for the JapanVisitor newsletter
Books on Tokyo Japan