Airtel — poor connection for calls and internet

Whenever i try to make calls with my old number [protected] they hardly go through even in over 15 attempts while with any of my new numbers the call goes through in 1 dial, why is this so? However, the network is generally poor in pan india and worst in hazaribagh and ranchi. Is the load too much for airtel to handle or there is some other issue with the number itself? Kindly check and resolve. Thanks.