Airtel - Regarding Airtel Network issue

i have an airtel postpaid connection... my no. is parent no. & it have * child no..
i have internet speed & call drop problem from last * year... i called customer care many time & file complaints but they just pass time... they ask for few days & no response from them...last time i file complaint on ** March ****... regarding that my airtel *G speed at this location is only *.* Mbps...while i used to get **Mbps speed at this location..they guaranteed me to solve this problem in ** hrs & ask me to renew the plan... i renewed my plan but they didnt solve problem... then i again called them then they ask to wait ** hrs but again problem not solved... then again i called them then they again asked for ** hrs.. now its about * months passed but my problem not solved... now today again i called them & they asked me that there is network congestion in your area & we need to work on it & it may take * months to * year...now i am sicked bcoz of them... if they tell me this * year ago i disconnect my airtel connection at that time... but they just passed time from last * year...