HDFC Bank — hdfc life policy no 90917011

I have a cancer care policy from hdfc life, his premium was rs 1825 yearly,
After 1st premium i study in detail about policy feature, i am not satisfied with policy, so i decide that i will not pay 2nd premium of policy
That's why i visit in hdfc life office for deactivation of policy, he said please sign mendate deactivation form after that amount will not debit from your account, i sign it and submit it, after that auto debit facility remove from my policy no 90917011, i got msg at that time for successfully deactivation of auto debit

But after 10 month on dated 29 march 2020, amount of rs 1825 again debit from my savings bank account. I complain it to hdfc life service team.. They clearly mail me that. Your amount is adjusted in your policy we can not refund it
My question is when i already submit request for auto debit deactivation then how can hdfc life debit my account who will authorize to hdfc life, and after complaint they clearly said we can not refund it,
Then why i sign auto debit form.
Request you to please help in refund my money