Read this too Airtel Customer Care
Airtel being India's largest Mobile network supports various Customer care services for its Postpaid services for mobiles and broadband uses.
Airtel provides 3 ways to its users to access Postpaid Customer Care
1. 24 hour access number - From any part of India, as an Airtel customer you have the convenience to access their 24-hr customer service number, from your Airtel phone either from mobile or landlines. You can find the Customer care number by putting your city 
2. Payment Assistance centres - Airtel also has many dropboxes and assistance centres in all the cities of India, though they are only meant to drop cheques and for bill payment and complaints, they can also be used for inquiring about various airtel services.
3. Airtel Relationship Centre - These type of centers provide easy facility to take a new connection or to subscribe to any of our value added services and get more information on them. These centers can also be used to pay your bill or get a new handset.
An example of the above services in the Delhi region are as follows
1. 24 hour access number :- a. Call 24 hour help desk no 9810012345. b. You can send an SMS to short code 121. c. You can email your questions, comments or suggestions at email@example.com. You will have to mention your mobile no. like 9810012345 in the subject of the mail without any space or any special characters between the digits for a quick response.
2. Payment Assistance Centers :- a. You can walk into any payment assistance centers to pay via cash or debit card. b. You can login to www.billjunction.com and www.billdesk.com for payment through credit card.
3. Airtel Relationship Center :- You can visit any of the Airtel Relationship Center spread across Delhi for your queries and getting value added services.