Airtel — lack of response

1. My post paid bill came with a free child connection which had the facilities of free calling & 100 sms free both local & on national roaming. However despite their self advertised scheme airtel for the past almost one year had been charging me a miniscule amount o[censored]pto rs 1/- for sms on the child number. While the amount is miniscule, it is a constant irritant, especially when your repeated requests to rectify the wrong bills is not paid heed to.
2. I downgraded my airtel postpaid plan to rs 649/- around 21/22 sep 2018. Ever since then, my amazon prime has stopped streaming & it gives me a prompt to subscribe to the service while the my airtel app still shows it as subscribed upto 30 aug 2019. Despite repeated requests made to the customer service executive & their supervisor, each time i call i'm told that the problem is at airtel's end & will be resolved shortly. I'm told to wait for 48/ 72 hrs after which too the issue remains unresolved.
3. I feel i've made a mistake by bearing airtel for so long. I'm planning to go for mnp to change my service provider. Can someone tell me whether the child number will get transferred to some other service provider too. Payment of additional money is not a problem, but i want to keep both numbers.