Airtel Prepaid — not allowing to change the service from Vodafone

Address:

Jalna, Maharashtra

My Mobile Number is [protected] from airtel. I found that this is not good service. Whenever I use to call some one I am not able to connect the call. there is nothing to listen while calling someone and after some time the message comes on screen as "call ended". I am not getting what type of horrible service it is. So I have applied in Vodafone store for MNP. They have sent my request to Airtel but airtel has refused to change my number to vodafone service stating that I have signed some agreement and I should report to Airtel customer center. There is no such center available in my city. now tell me what shall I do?