billing cycle is when you reach data limit usage it will either warn you or turn off the internet connection and save you from deducting balance from your account. we don't need it anymore in india most of us have unlimited data plan.
that means it's connected on 2g network . go to settings and change mobile networks to 3g, see if you're getting 3g signal then change back to auto LTE/2g/3g. maybe there's some issues with network coverage in your area. you can go outside and check.