The rules are different for business customers and consumers under many rules, E-SIGN included. But I would ask what is in your current agreement? Hopefully it specifies certain methods of contact. I've never agreed to text message contacts with my bank so if I received one I might dismiss it immediately as spam. If your customers would do the same, having never consented to this form of communication, I'd say your change notice would be ineffective. I would use only a commonly approved and accepted method.
Reflecting on a case of account takeover, say you text the link to your customer and they follow the link and all is good. Then they get another text from "your bank" with a link requiring a password change for account access. Should they follow it because this is a way you communicate change? This message is from a hacker who wants logon info for an account takeover attempt. So they should not. But you can see how this could be confusing.