SMS sent without my consent from my Redmi 7A phone?
According to quick research, the "ACTA" SMS is used by ICICI Bank for a verification/activation message on their mobile apps (e.g. iMobile).

From Mi Community - Unable to activate icici i-mobile app on my POCOFONE F1,


  Post #10 
  
  Solved after the solution given by the online imobile team.
  During the activation process,  you get some random text message (ACTA *** which need to be sent for verification) , you copy the entire text and send the same to 9215676766 instead of +91222208888 (icici server number which is usually busy).
  This sms need to be sent within 90 seconds and jump back to imobile app and proceed with the activation by setting 4 digit pin and grid value verification. [...]
  
  (Emphasis added)


Also, thanks to the OP for confirming it on the comment thread,


  I then called ICICI Bank customer care and the representative has confirmed that this number (ed. +9184220...) belongs to their iMobile servers and the message is some kind of legit verification message required by the app to function properly. Earlier I must have clicked 'Allow this app to send SMS' so the whole process happened automatically.