How can I mix two differents I cloud ID?

HI!, I HAVE MANY PRODUCTS FROM APPLE,

IPHONE 6 -128GB IOS 9.2

IPHONE 6 S - 128GB IOS 9.2

IPAD PRO - 128GB WITH CELLULAR IOS 9.2

Apple Watch 42mm 2.2

OLDERS, I HAVE ALSO:

IPAD 3RD

FIRST QUESTION IS:

I HAVE TWO DIFFERENTS ICLOUD ID I´D LIKE TO MIX OR MAKE A FISSION OF BOTH ACCOUNTS, PLEASE HELP ME TO DO IT!, THANK YOU!

SECOND QUESTION IS:

WITH MY IPAD PRO 128GB WITH CEL PHONE, HOW CAN I DO MAKE A PHONE CALL USING THIS IPAD, CAN YOU TELL ME IF I NEED AN APP OR OTHER WAY TO DO IT PLEASE?

THANK YOU AGAIN.

PATRICIO REY S.

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