Here's how you can Send Whatsapp Texts to Numbers with out Saving in Contacts :
=> First of all you need to download an Application to start this process it's name is Click2Chat, You can download from here.
=> You can also find a "Send Later" option in Click 2Chat application which allows you to Schedule your texts which is available to many.
By using this application you can send Text to a whatsapp number without saving to your contacts and also you can Schedule your whatsapp texts as well.