Microsoft Lumia 640 XL :- not able to add 2nd phone number to saved contact, why?

[Windows Central Question]

microsoft lumia 640 xl :- not able to add 2nd phone number to saved contact

mobile :- microsoft lumia 640
I am not able to add 2nd mobile number to the contact list, i am not able to find any option? plz help how to add new number to saved contact list