Thank you! Although my Galaxy Light running 4.4.2 doesn't have that setting, I think I solved it by turning off the setting to automatically insert my local area code. What seemed to be happening is that when I launched Phone, for some reason it searched my contact list to display the name and number of the first contact that matched that area code, which was most of them. After disabling the auto area code, there has been no preset number (at least not yet).
Thanks again for your speedy reply!