Bharat Sanchar Nigam [BSNL] — deduction of amount in name of services i didn't even subscribe for

I received two messages on 5th may 2019. First one was from
57171 that "you are subscribed for service silver screen for 30 days. To unsub send sms stop to 155223 (Tollfree) or dial *777#. Thanks for using bsnl services. I received another text message from bsnl exactly at the same time stating"dear customer, your account has been debited with rs. 30. Main balance...".
I was really disappointed & upset as it was not the first time it was happening. I have been charged rs. 30 twice this year without me subscribing to any service at all. There is not a chance that i pressed any button to subscribe to any of them as both times my phone was on a table put on charging.
Please note that when it happened first time, i called bsnl customer care immediately that i do not want any such service. They offered me to unsubscribe it. When i inquired if i would receive my deductedamount back in my bsnl balance, they just denied it.
So how to stop this all as i am being charged without my authorization every time.