Airtel — making an outgoing call shows invalid number

Address: Indore, Madhya Pradesh

From last 2 days when i am calling on a airtel phone number it shows invalid number i dont know why it shows that, please sovle my problem as soon as possible.
Otherwise i will port to other provider.
I am not face this type of problem before it is first time for me. Kindly solve my problem as soon as possible.
Please sir/mam i get more problem by it.
Please solve my problem as soon as possible