I am having the same thing with the contacts, it;s very annoying.
But , if you call from the "People" ( and you have in view just the phone contacts ) the last dialed number will appear in the "phone button list " .
Also, see here my open thread, maybe you will find some help
Also, if your phone it's new, how is you battery life ?
PS: if you find a good battery monitoring app please be kind and send me a message
Thanks a lot!