Dual internet connetion

hello everyone,
i have 5mbs/unlimted internet from my cable oprator in mumbai.it works very well normally. but from last few days i am having lots of disconnetion maybe be because of rains. so i planned to keep one backup internet connection and bought airtel home wifi with plan of 1000rs for 10gb data per month. i know that it is very easy to connect both to my system and run but i want to know that is their anyway that it can keep switching to one another if one lost the connetion. i dont want to use airtel wifi as base connection because it will use huge data and i will be charged heavy. so i want to know can i use my broadband as base connection and when ever my base connection is down my pc can switch to airtel and when its up again it can switch back to broadband?

thanks

Dual internet connetion