dialing number from contact list

[Cabs]

Galaxy J7 Prime just purchased and loaded tel # from old phones and synced with outlook from the computer. When trying to call using the phones contact list messages pop up saying Mobile network not available even though it is a landline number and Not registered on Network message for other numbers. I can dial and connect by using the dial pad. Any suggestions?

I am New to smartphones!

[JessL]

Is there an error message for all the numbers in your contact list?

Also, are the numbers appearing in the contact list in the same format as the ones you're dialling? 

[Cabs]

Not in all contacts, some landlines and some mobiles.

I believe all contacts are in the same format.