My SSH file : ~/ssh/config :
Hostname sftp- customer_loves_security.fr
To connect :
Prompt then asks for password
Script example to upload a "test.txt" file , using «expect» :
/usr/bin/expect << EOF
spawn sftp customer_loves_security
send "cd deposit_folder/\r"
send "put ./test.txt\r"
Because you're not in charge of your customers usage of ssh, given you have more than enough dealing with your own ;-)