Whatsapp has changed the way we communicate, there's no doubt, every day and send less SMS send a SMS to a friend abroad is so simple and free with Whatsapp that has become almost essential.
But like everything in life, when it works well it can be a real headache.
Sometimes it happens that you want to send a message to another person that you know is on Whatsapp but do not get contact with him. This is because the number of your contact must be saved in international format (eg, for a number of Spain would be 0034XXXXXXXXX or +34 XXXXXXXXX).
If you have jailbroken your device, you have to be careful not to be installed from Cydia NET package -. Local Number Format, if so you may have trouble using Whatsapp too.