First, please try to understand the difference between SMS banking and SMS alert service for your bank account.
SMS banking is accessing/monitoring your bank account details and making transactions through your mobile SMS. Once SMS banking service is activated by your bank - you can start doing activities on it.
Whereas once SMS alert service is activated by your bank upon your request - you do not have to do anything; you just keep receiving SMS about your bank balance, information on certain transactions and some other important banking alerts.
Method of requesting the bank for activation of SMS alert service:(1) Go to the bank's branch office - collect the application form for this - fill up details, sign and submit it there.
(2) Carry a written signed request letter, which has all the necessary details about your bank account for identification and submit to the bank.
(3) Some banks are providing options for alerts activation through their online net banking portal.For writing a letter to the bank and submitting your request, the following format is for your reference.