How do I cancel my airtel black plan?

Lore: I've been using airtel black for abt 3 months which has dth and a few otts included with wifi...after we got ott stuffs, and a new tv, dth has no use in our household, nobody watches channels here anymore, so we thought of switching to another plan where wifi is 100mbps with otts including netflix, prime (for just 1 yr), jiohotstar, apple tv and many more and no dth...we thought they'll switch it as it is...but they came and switched the whole modem, and disconnected the old modem and said the airtel guys will come and get it back...then the customer care guy called and I said the lore and bro said I need to pay the bill amt due till the date of cancellation and then they will come and take the modem and the set top box...he said the due amt was 1.4k and I was flabbergasted...and I inquired why so high and he said we might have subscribed to some channels accidentally coz u click once and they'll be subscribed...I also believed it but said I'll pay after I reach home...thankfully I was out of town...then suddenly I remembered that the outstanding amt was 900 or sum in my airtel thanks app ... And yeah it was only 931, and I suspected the guy and asked him to give me the bill...he said wait and he didn't send any, again asked me to pay the amt...I stopped responding to him...now I get 2 to 3 calls everyday to pay the amt which is so frustrating...if u think I can just ignore those calls, my profession is junior advocate(yet to be enrolled) and I wouldn't know when some client from our office would call me, so I can't just ignore unsaved numbers...

If someone knows how to cancel it properly, pls let me know...

Thanks in advance🙏🏽