What could be the reasons for two different OTP messages for the same merchant when we do online transactions through debit card?

While I was doing a transaction (say adding money to one of the mobile wallets) through a SBI debit card, I could see two different OTP messages for different transactions. (Please refer to the image)

Say one time I am adding X amount, So I was getting OTP message from SBI but in the next transaction when I was adding Y amount, I was getting OTP message from BHIM SBI Pay.

What could be the reasons behind it? Is it becuase of the payment gateway (Like PayU,CC Avenue) or somethineg else? Has anyone else observed the OTP message coming in the name of BHIM SBI Pay / SBIPAY? AD-SBIPAY

TM-SBIOTP