State Bank Of India [SBI] — About security and verification

Address: Pune, Maharashtra

Website: Sbi

I mostly use my debit card for online transactions but recently I have noticed that suddenly I was not getting the transaction message on mobile number. Even after that login page is also said that ur number is not the registered mobile number. I don't know how automatically I have lost my authentication. Please can you tell me reason??
I am asking this because previously there was a case of hacking ( someone sends u a message like " u have won coco-cola prize of 1, 00, 000 please send ur name address for receiving prize." ## and Even when u have not sent any details still someone enters in ur account. ##)
I also got the same message and 2-3 days after that I have lost authentication.
Please check this security threat and tell me the correct reason for losing authentication.

Thank you.