Hi, @VisnjaBravoBeba. Welcome to the Community, and thanks for reaching out! Did you happen to read my previous post within this thread that is marked as an Accepted Solution? It outlines some considerations, and the steps to take to look into moving your account from a trial plan onto a paid plan.
Please keep in mind that not all requests to switch to a paid plan are granted. As well, higher support demands mean that it can take longer than usual for your account to be reviewed for eligibilty. Therefore, if you don’t have a lot of time left on your trial, I recommend waiting until your account automatically transitions over to a paid plan as a more efficient measure to being able to edit your SMS Notifications. However, if you would like to move forward with the review anyways, please visit the Shopify Help Center and log in to your account to create a support request. We’re currently unable to assist here in the Community with account-specific requests like this, therefore we'd be happy to continue helping you through live chat, email, or callback instead.
I hope this information helps. If you do have any further questions or concerns please let me know. All the best!